Took the tank off the RZ for lining and 2K clear coat. Not to make it pretty, but to make it hold gas fumes inside instead of bubbling up the paint in a couple spots. Also, ordered a new needle from Toomey because the left one looked a little chewed up. Installed that. Put it all together and rode around the neighborhood.
The YPVS had previously been a little off, so I got it lined up before ever taking off the tank.
While rolling on it in 1st or 2nd, it seems to bog, (or be missing a lot of torque). Then suddenly, about when the YPVS should have done it's thing and is getting out of the way, there is a sudden torque hit. I mean light switch sudden. Learned to lean over the tank just to compensate for that.
Got back to the house (twice) and the YPVS is full clockwise with the engine off. Should be at counter-clockwise "home" position. Turned the key on and instead of 2 moves turning clockwise to open and then back to home, it makes three moves and DOES find home position by itself. Both times. Seems like it should be fine. Why would something go wrong?
Then, what did I do? Maybe disturbed a wire? This was a carb and tank related exercise. Maybe #1 and #2 YPVS cables became too tight and caught up with me?
If any clues, please let me know.
If something disrupts the bikes battery power or the bike stalls the powervalve may sequence differently. Cable adjustment should be take up the slack and then back off the cable adjusters a 1/4 turn to prevent any drag.
your power valve controller sounds like it took a shit, or the servo is having an issue (if the wiring mentioned above is all ok).
hi,
if it turns out that the control box is toast (ive had one go after a reg/rect failure) there is a guy in Greece who repairs/modifies them with a switch box to play with the valve timing, i highly recommend him, did a great job on mine.
https://www.ebay.co.uk/itm/277019422206?_skw=tzr+power+valve+controller&itmmeta=01JW886RNA7RZYH9H1R5QJ0Q72&hash=item407fa4edfe:g:kpAAAOSwy4hUR7Y5&itmprp=enc%3AAQAKAAABAFkggFvd1GGDu0w3yXCmi1eTynOTiN6ENN%2FDnZ4OWn%2FNLKHjJkPx3P9x7WNN2wEoXej1sR2THJwulVimrA7ZRUp0uAXtixK4jx%2BdjtPQjybO%2FZFp5tmxOdPqaehYqVbsqROe3%2Bnl%2FPjagS8Vof%2Fi3vkwqTab2hfZ5YCbWYL54bNZ5v4wmFzZB2FJBsP%2FWSbY98ft5yq6V98xhpLtCletkJcwwzHTHO9DMsBSCh6RhSVjBtL6Rt7WicBFtzfrXPq4gAJOVkzkCcI%2F8YTllPvIUsm10o0Rrvm5wGpn8XSUVC8N9fTI8Ris64BK%2BABm8Na0PREEe24936QlXG5t%2B3vFzJU%3D%7Ctkp%3ABk9SR-iKm4jiZQ
cheers
les.
Loosened up the cables a bit and checked that it was coming to rest in the right place last night.
The bike didn't stall out, but almost did on both rides. I could hear the YPVS hunting around as it was idling way too slow. Hoping that's what the prob was. Will have to report back later.
Also seeing where someone replaced the transistors on the board and "restored" the controller.
That looks really good, Les. Simple programmability, too. Priced pretty good for that. Thanks!
if you're still running a stock cdi as well, just get a zeeltronic that does both. 40byear old electronics are time bombs. 0.02
How old are the PV cables? when I had to rebuild my PV assembly due to O-ring leaks initially (also found slop where the clamp mated halves together) and reassembled everything according to the manual. I lubed the cables like I always did with other cables and they slid easily inside the sheaths. However, I couldn't get everything to stay adjusted correctly after multiple tries and test rides.
Did some more digging and came across instructions for a "drop test". Hold cable vertically, pull wire all the way up, then see if wire drops by itself with no friction/restrictions. They did drop but tiny bit slowly. I bought new cables and repeated drop test- comparing new vs. old and it was night & day difference. Installed new cables, adjusted everything per manual and it worked perfect and never lost adjustment again. Couldn't believe that little bit of restriction in old cables made THAT much of a difference but it did!
The cables have seen better days, I'm sure. Sounds like a concern that should be addressed.
Hoping that Zeel money won't have to be spent...
I'll be taking the cover off and revving it to watch valve movement, too.
zeel money is smart money spent. :twocents:
Quote from: m in sc on May 28, 2025, 06:23:15 PMzeel money is smart money spent. :twocents:
You can increase the area under the hp/torque curve, right?
I'll tear into the carbs again, just to see if something is amiss. YPVS seems to be moving appropriately. Carbs were synced mechanically, (although the right slide has a longer overall stroke length :huh:) Gonna compare the carb internal lever lengths to see what gives.
Always room for an error on my part.
...hits so hard on the power band.
yes you can move the pv positioning and timing curve. also, programmable rev limit and add a shift light. when I got my tzr was the 1st thing I ordered even though the stock stuff worked
40 year old electronics, sorry Heave. You should probably blame the guy who sold you this turd.
As a side note, Steve and I were at the same college 45 years ago so we go back a ways. I sold him the above RZ last summer, and I reserve the right to make fun of him when he has trouble with it. Having said that, I pray the ancient electronics turn out ok so he's not forced into zeel money. Rock on Steve, keep us updated.
Oh, it ran great until now. I'm into the carbs and everything is looking fine - so far. Double checking needle heights later, but they were sticking through the mains the same on both sides.
The power valve cycles and goes closed when it starts. Then, doesn't really budge until rpm goes to the power band range. Maybe I'm missing the opening steps in between.
Would be cool to drop in a known good YPVS controller to check before spending the dollars.
So, not discouraged, just feeling challenged. It's an old friend that needs some new parts.
they work till they don't. I remember..12? 15? years ago, or so, the kaw triple guys saying the cdis were bulletproof.. till they weren't. we just went thru this w Josh's 85. it had 3 issues, one was the pv controller, the other was a bad stator. THAT was fun to diagnose. also throw in a missing half moon c clip for the crank. :huh:
Mine with a Zeel controller cycles when you turn the key on and seems to come back to where it was with the key off. Start bike and it hasn't moved. At 5000 it starts to rotate, 6000 and away it goes and really cranks open.
Quote from: 1976RD400C on May 30, 2025, 12:44:53 PMMine with a Zeel controller cycles when you turn the key on and seems to come back to where it was with the key off. Start bike and it hasn't moved. At 5000 it starts to rotate, 6000 and away it goes and really cranks open.
Actually, that might be just what mine is doing with the revs going up.
I'll watch it while having someone else rev 5 - 6k.
Will raise the needles back up 1/2 step too.
There's still the possibility that it's something stupid simple.
My '74 H1 CDI went bad. I was in college and electronics nerd Ralph down the hall fixed it for me. He had me pick out all the potting first and attained instant hero status.
I forgot about Ralph and the resurrection of the H1 cdi box. I bet not many people try that route.
Assembled everything after going through the carbs again. Terrorized the neighborhood and starting to conclude that a cylinder must be dropping out. Starts/idles great, struggles through the low range (apparently on one cylinder) and furiously breaks loose from 6000+ rpm.
Plugs look good, they are gapped right. Left cylinder on the temp gun is a little cooler.
Not the coil, I assume.
Once the drop-out starts, it doesn't recover until the higher rpm.
Will look behind the left crank end cover just to do something.
Off on another path.
Does the RZ have ignition timing control that could have a segment of rpm drop out, due to loss of output?
Thank you guys for the seasoned suggestions!
Matt, this bike is too beautiful to be a turd.
again, did this recently. 99% sure on that the stator was going. swap could leads see of it follows.
Mark, I see your post on swapping leads and don't know what to swap without changing the wrong thing.
I envision doing that, having the same problem but with the other cylinder, and verifying with the temp gun. Then, not knowing what to look for to fix it.
if it does that its either the plug leads, plug cap or coil itself. since rz coils have the wire encased, its sort of a 'if the wires bad the coil prob needs to go'.
... keep in mind, the 1st thing i did when i got my tzr was get a new coil and zeeltronic right off the bat even though the stock ones worked well. i don't want to find out on a ride. i say this because i want to illustrate that i practice what i preach. 40 ish years is about the life expectancy of these components, it just is in my experience.
:twocents:
Ordering a coil assbly, plug caps and YPVS cables from Yambits before doing anything else :thumbs:
RZ plugs are supposed to be BR8ES.
Mine is running B8ES, but with 5kΩ caps.
*** 5k NGK resistor caps OR resistor is the same either way? ***
Don't want to overstress the coil - if that's a thing.
Yambits shipped Monday. Stuff arrived Wednesday, FedEx. They are hitting on all cylinders.
New Yambits parts did not help. Left cylinder seems to be what drops out - it's a little cooler after the laborious ride in the neighborhood and the plug is wet while the right is dry. New Yambits "stock" coil, which includes wires, and new 5kΩ caps.
Idles fine, struggles while loaded at low to mid rpm and then it's serious rocketship time at 6k or so. Kinda hairy.
Plugs are B8ES, (not BR8ES like the manual says - see question in the post above), and they ohm out/show continuity like non-resistor plugs should, gapped and looking like new too.
I have a 1985 52Y cdi, but it is 40+ years old now. YPVS under observation looks like it is doing exactly what it should.
Having the understanding now that both plugs fire every 1/2 rpm, the bias toward the left side struggling to fire is a mystery - UNLESS there's a problem with triggering during the timing of the left cylinder. Why it fixes itself just in time for the power band is :huh: .
Left cover comes off next to look at the flywheel trigger sitch. Maybe some of you brilliant dudes or chicks know something. [Remember Heather Dakota Gurl?]
I had an RZ back when it was fresh and new. This one, at 40 yrs old, is a learning curve.
...DO I NEED a new left carb "choke"/enrichener assembly? It looks like it's okay, but is original and seen better days.
Matt, I'm pleased with the result of your rebuild. It's well assembled and tight.
test your stator windings.
Steve hope you can narrow down what's going on. I don't even know what to suggest other than throwing parts at it. You certainly need the advice of this forum cause I'm not smart enough to help you. Keep on, you'll get it sooner or later.
3 stator windings seemed to settle at 0.2Ω across each other at 75F, 3 white wires.
Consistent, but not the 0.4Ω that the book says at 68F.
Seems ok.
Gonna order a new enrichener-knob assembly since it seems to be the left carb. Cheap from eBay. Not counting on it doing any good.
you measured the charging system windings, not the ignition windings.
Assuming (guessing) that I check resistance across the "High Speed Charge Coil" and "Low Speed Charge Coil"
Maybe Red across Green and Brown across Green?
Manual doesn't define which is high and which is low:
yes, check all those.
the 2 whites 'together' are (alternator) battery charging. high speed and low speed coil are what you are looking to test. they call it a charge coil because it charges the capacitor.
I don't have that 3 conductor plug with red, green and brown.
There are separate green bullet, brown bullet and red/white bullet connectors.
Green to brown should be 2.55 ohm (according to the manual with differences from my reality) or 225 ohms, per some web post.
Mine is 132 ohms.
Brown to red/white (not just red) that does go to the cdi by a different route is 8MΩ. Presumably, should be 5.33Ω.
That could be the smoking gun. Confusion is the thing though.
Maybe someone threw in a workable stator from some other year.
What's the best route for a drop-in stator to try next?
get it rebuilt by Rick's. it's done. same exact issue josglh had w his. expect to pay 380 ish
Found this. Would have helped with the plug and red wire confusion:
"The 1985 31K has changed Stator and CDI. The CDI is marked 52 Y-50. The 52 Y-50 CDI has also only 8 connections (the other two to have 9).
This CDI is missing the black-and-white cable, which serves to turn the engine off by the kill switch. The 85 stator is marked ÈZ or 8DX. The stator has two somewhat thicker load coils.
Safe distinguisher of the 85 stator is the red-white cable at the load coil, which is always red with both other stators! A further indication is the missing connector for the "load coil", which turns into three individual plugs (brown, green and red-white). The Rotor has the marking 51L."
Steve, guy selling a Vape ignition for 300 bucks in the for sale section. Guessing you've seen it...
Saw that, but looking at it today, I see, per Mark, that it would work on the RZ after all.
Have no clue on compatibility with stock CDi and future compatibility with CDi and power valve module changes.
Lack of knowledge is an issue here. Looks attractive to me.
it should bolt right on. however, remember there's no keyway so it will need to be positioned.
I'm in.
Will need help with positioning method when it arrives.
Degree wheel, or just dial indicator on piston(?)
Thanks for the heads up, Matt
and the endorsement, Mark
i do it with a dial indicator.
I do see some toastiness.
I don't see how the VAPE talks to the RZ CDi & power valve control.
Looks like it's for an RD.
Am I missing something?
Geez I hate to be that guy but I've been following this thread outta curiosity and yeah that set up diagram is what I used for my 75' RD250 and I have seen that Vape ignition listed here in the classifieds. I thought it was a good deal cuz it is but for the RD. Just getting on the Economy Cycles site I see specific complete Vape ignitions for either the RD's or RZ/Banshee's and you're on there you notice different SKU/part numbers. To make it more confusing...here's a link to the Vape site that list some of the different systems they offer for Yamaha bikes. Good site to bookmark there is also install instructions. https://www.vape.eu/yamaha?page=2 (https://www.vape.eu/yamaha?page=2)
Yeah I dunno, way over my head...I'm just looking at those assy. instructions and corresponding wiring diagrams. Looks like you pasted the correct one based off the part number listed but it seems like Vape just uses the same diagram for all the RD models they offer. Oh well a lot help I am. I do notice that they indicate one system that works for RD's and Banshees taking note of a longer crankshaft.
Yeah that one set of coils looks a little crispy. Acting as your useful idiot of a friend, I have a dial indicator that screws into the spark plug hole if you need to borrow one. Easy to send.
I have the cool indicator setup from Economy Cycle, Matt. It has made my life much easier with the RD400 points timing.
RDryan, I tried to be accurate on that product number and web schematic. The main number, 711379900, is the same. However, the one that snorkelfork is offering has an extra "-102-4" at the end of the part number. Don't know if that makes a difference.
This could be a bust. He plans to look into the included schematic and get back to me. snorkelfork is a good dude.
the powervalve controller and cdi are all based off ignition signal. it will work, period. will it wire right in directly? no you need to get the signal sourced. the easiest way is.. get a zeel and wire it all in at the same time. OR reach out to vape. Imho the best thing to do to KEEP IT SIMPLE is to get the stock stator repaired. or, contact vape and ask for a schematic. but you're going to have ro spend some money one way or the other
It's a pay less now on stator repair with some delay to get it running AND pay more later when something else fails (because there's no "Ralph" a few doors down anymore).
At work, I find overseas communicating to be problematic.
Yeah I see, Mark.
I'll check in with snorkelfork.
Life's short and I have limited time to spend in the garage. Since I might tragically die some day, a Rick's rewind looks like the thing to do.
$800 for NOS on eBay.
yeah. but nos is still 40 yrs old. avoid it imho
:agree:
Get a Rick's. Better than NOS for a couple reasons. As Mark mentioned, the NOS has been sitting around for decades while the Rick's is new. Rick's stators are also better built than OEM. I bought one a few years ago for one of my bikes and it's really nice.
Yeah, I see they won't take it back so that could be a nightmare - and they want too much.
This does look interesting, though: https://www.ebay.com/itm/154287303614?
That said, I filled out a Rick's part repair form to print off and send. Gotta respect our US business peeps.
this is deja vu to joshes rz, even considering the overseas one. Tim, if you're reading this... right?
Yes it is...
Josh must be an alright dude :dawg:
Was there a thread on his terrible plight?
I did err by titling this one with "YPVS".
Appreciate everyone helping out!
there was not yeah hes a great dude but was super super frustrated. and rightfully so. this was also on a freshly rebuilt motor and a fresh painted bike etc. he poured a SHITLOAD of time, effort, money into it doing everything right... except that. and now he is literally just waiting otn eh stator to get back, should be Monday or Tuesday
mnein just rebuilt the engine and brakes on this one. What could possibly go wrong with 28k miles, multiple wipeouts and 40 years?
Would be nice to see a photo of Josh's if he's willing to share - so we can drool.
sure.
i realized i hadnt uploaded any '25 deals gap pics, so i uploaded them just now. we spent all week trying to diagnose it.
(https://2strokeworld.net/wp-content/uploads/gap-all/gap-2025/20250507_192857.jpg)
weeks before, we had it at the house after it blew the motor, right after the rebuild trying to sort it out then as well. carbs, ignition, jetting, swapping parts etc. I always 'felt' it was the stator, but took a while to confirm.
(https://2strokeworld.net/wp-content/uploads/gap-all/gap-2025/20250507_141419.jpg)
(https://2strokeworld.net/wp-content/uploads/gap-all/gap-2025/20250518_125547.jpg)
Thought that I replied that the paint looks excellent!
So, 2+2=4
That bike is an '85, it's 40 yrs old. Mine's an '85. Apparently, the winding protection lasts 40 years, period.
Rick's must be seeing a lot this year. They have mine, but I haven't heard back and might not for a couple weeks.
Photo of that red RZ in the garage looks tasty.
yeah thats in my garage trying to figure out wtf was wrong w it in april. i think they had joshs 3 or 4 weeks. He got it back and has ridden it every. single . day . since. ....And is smitten. I ruined that poor boy. :devil: :clap:
My original stator is hanging in there, but the previous owner told me the controller blew so he installed the Zeel.
Schematic
Quote from: m in sc on June 30, 2025, 09:35:17 PMHe got it back and has ridden it every. single . day . since. ....And is smitten. I ruined that poor boy. :devil: :clap:
I understand the smitten thing. He probably has more power than me, but I had forgotten how that torque felt. I'm smitten by the power valve concept.
Matt put a fresh 15T front sprocket on too. I'm sure that's part of what I like. Seems just right for an RZ.
RD400C, that Zeel schematic sells itself.
Rick's called today. My stator actually checks out fine. I'll be looking at some wiring beyond the stator pigtail on the RZ to see if there was an open somewhere in the red/white wire.
I'm thinking to get them to rebuild it anyway because of age plus that caramelized burnt look; while also assuming that there's a possible problem in that red/white wire since I measured closer to the cdi box instead of the stator pigtail.
Is there a transistor in the cdi bad? I dunno.
How's Josh's stator now?
Did his look toasted?
looked perfect actually.
Well crap. I suppose it would be better if they had found something wrong with the stator, then you at least could point your finger at something.
Quote from: mnein on July 10, 2025, 08:44:46 AMWell crap. I suppose it would be better if they had found something wrong with the stator, then you at least could point your finger at something.
Yeah, that threw a little wrinkle into things. I tested that red/white wire that I had used to check the winding with high ohms last night. It was fine.
Planning to call Rick's and tell then to go ahead. I saw that dark brown insulation and it did smell burnt. Seems like something might be intermittent and shows up fine for them, but not real life dependable.
Quote from: 2steve on July 10, 2025, 09:03:42 AMQuote from: mnein on July 10, 2025, 08:44:46 AMWell crap. I suppose it would be better if they had found something wrong with the stator, then you at least could point your finger at something.
Yeah, that threw a little wrinkle into things. I tested that red/white wire that I had used to check the winding with high ohms last night. It was fine.
Planning to call Rick's and tell then to go ahead. I saw that dark brown insulation and it did smell burnt. Seems like something might be intermittent and shows up fine for them, but not real life dependable.
Good call IMO. In the past I always had terrible luck in situations like this. I'd figure "OK Great! Experts said it's OK, so I get off cheap". Then get it back together and seems good for a bit before it fails for good. Lesson learned the hard way :bang:
yeah. man I hope I was right and didn't cost you unnecessary funds. but, at least when it's back (and I'm pretty sure that's the issue) you'll KNOW
Joe@Rick's is on it. They are to call for my credit card info.
$360, but a big step forward in troubleshooting and peace of mind.
Hoping to feel that rush of RZ torque again.
In the meantime, there are plenty of little things to do.
Either way, Mark, I appreciate it.
for me, peace of mind is worth it. like said we went thru every last component Josh's
It seems at this stage of the game you gotta do the stator dance. Heather will understand.
Quote from: mnein on July 11, 2025, 08:12:39 AMIt seems at this stage of the game you gotta do the stator dance. Heather will understand.
She knits, using expensive yarn. So the understanding is built in. If her friends ask about a shawl, they have no idea that just the yarn cost is over $120. It's therapy. She knits so nobody dies.
lol. my wife has horses that cost way more $ for feeding, vet bills, etc. than all my cycle projects combined so I never hear a word about my hobby being expensive :vroom:
My wife: "I thought you said you would be selling some of your bikes, that never seems to happen"
exactly! I've heard that so many times before, so I list each bike I sold in the previous year. oops, forgetting to mention the new ones I replaced them with :dawg:
Stator is making its way back from NH.
I got distracted by the gauges. They look like this:
20250720_174707.jpg
Diablo decals will get them looking like this first attempt as long as I don't mess things up:
20250720_152825.jpg
Buying some Testors fluorescent orange to turn the middle strip on the bottom side of the needles back to orange instead of faded white.
That must mean that I'm optimistic that it will run right soon.
Hey Steve, just got back from vacation. Hope the stator cures things, and rock on with the gauges. Them there are hard to replace. My wifes hobbies do not come close to costing as much as mine do, but we have some working understanding on financing of said hobbies.
Gauges look much better with new Diablo faces and the needles painted fluorescent orange.
Rick's did a good looking job on the stator. Hope that is the true cause of the low-mid range running problems.
Rewound stator is in. The problem is 30 - 40% better, but still there. Wondering about plugs and jetting, since the coil has been replaced with new.
OK to run non-resistor plugs AND non-resistor caps with the stock cdi?
Neighbor stopped me offering to buy it last night.
yes you can do that. same thing Josh ran knto.. reset jetting to where it was and spot on
The pilot now is one size bigger than Toomey says. I agree with that, since the air screw can just be opened up to 1.5 turns to make it right, but maybe I'll go with their size 20 at 1/2 turn out. They did all the research after all. Maybe drop the needles 1/2 to one step.
Just rebuilt, so rich was ok, but might be a problem now.
I'll get new non-resistor caps and new non-resistor plugs.
... and do everything at once, so if it improves, I won't know why.
Here's what I learned messing around with mine for 3 years. If you change the pipes and air filter, they develop a bad flat spot at 5000-6000 rpm. You can hear it through the exhaust and intake tract. Jetting doesn't help it. I did pretty much fix it by installing UFO inserts in the carb slides. That required machining on the bottom of the slide to get them to fit in there even though they said they were for a RZ. Mine has resistor caps and spark plugs. I tried non resistor plugs, no noticeable difference. I switched from K&N and Y boot to individual foam filters, better top end power. I have the Dynojet needles and 410 mains. Didn't notice any difference from 360 mains. My PCDI-10VT is programmed same as a stock CDI, 27.5* at 3500 going to 17.5* at 9000 and 9* at 10000. If the power valve sticks and won't open up, it still runs ok but the top end power is not there. Those UFO inserts on this bike and my RD make a huge difference in throttle response, especially in low throttle openings.
^^^That's a help. I noticed that flat spot. It was ok enough, then it got worse. The thought was that it's a YPVS transition problem, when it was partly/mostly(?) the stator.
Assuming, like the RD400, you put UFO's in and you're pilot size MUST go down. With a 400 and boost bottle, way down.
Do you have size 20 pilots, or smaller with UFO's?
All good info. Thanks! I have UFO's that might fit:
For the RZ I have 15 pilots with the air screw at 2 1/2 turns. That feels right. I'm experimenting now with adusting when the power valve moves using the Zeel.
heres my advice: you did a repair. set the bike up how it was before and see if its back 'to normal' if its not, you still have something else to address repair wise. get your baseline tuning on the carbs back to where it was, period,. . don't change stuff now or it will never get diagnosed.
get the plugs sorted out, set the carbs back up they way they were. assess from there. ( and no, resistor plugs and caps or lack thereof shouldn't change anything. IF you have to run resistor plugs, run non resistor caps. they do have them. )
Id still be leery of the cdi box or coil. the " '30-40' percent better" tells me you haven't completely fixed it yet, and ufos aren't going to fix that. :twocents:
Yeah, gotta think on that. Carbs really are where they were, just don't know if being a little rich pilot/air screw/needle is a factor in this. It did run very well with this same setup previously (with that 5 - 6k flat spot that it would push through ok).
It has the same lower rpm symptoms to a lesser degree, but is no longer lighting up consistently at 6k or so. Just acts congested, then overcomes it in a less predictable way now.
Would be nice to be able to health check the cdi.
replace it.
John @ Economy has a Zeel stock RZ replacement. Might not be too much to handle. I'll just need to be a wiring boy with cool new tools.
RegulatorRectifier might have too.
Plugging in a known good one to check would be convenient.
I know the original 52Y cdi's are 40 yrs old, but are they known to be failing?
get the cdi and powervalve controller unit in one.
Steve - the 52Y's were obviously the good ones, the other part number cdi failed within the first 5 or 10 years of new. Unfortunately I don't know anyone that can determine the health of your cdi, maybe impossible, so I suppose you're doomed to replacing electronics until you find what's wrong. Working on a car right now that has intermittent starting problems so I sympathize a little with your pain.
yup. my 84s cdi died in like 09 or so. if you plan on keeping the bike just replace it.
Planning to keep the RZ till someone has to pry it from my cold, dead hands :dawg:
Mark, seems you did better than most if it wasn't till 2009.
Presuming I can use the Zeel that has both controllers inside with the stock stator and stock coil?
Matt, if you are stumped, do what I did and call three-finger Bill, (Shari's cell number). That boy knows everything.
In my case, the '90s Chev pickup needed a new ignig switch.
Glad I got a quarterly commission check recently :thumbs:
yes you can wire it in with stock stuff. get a new dyna coil as well
If you decide on a pcdi-10vt I would suggest the wire connection plug kit that Economy sells so you can add those on the controller wires and just plug everything into your existing harness (plug and play). Also the handheld programmer.
Quote from: 1976RD400C on July 31, 2025, 03:02:21 PMIf you decide on a pcdi-10vt I would suggest the wire connection plug kit that Economy sells so you can add those on the controller wires and just plug everything into your existing harness (plug and play). Also the handheld programmer.
Can you provide a link to the proper kit to order from Economy?
Thanks
https://www.economycycle.com/product-category/yamaha-rz-350/electrical/ignitions/zeeltronic-cdi-ignitions-controllers/accessories-zeeltronic-cdi-ignitions-controllers/
And a Zeel cdi+power valve box is on its way from Granbury, TX. :thumbs:
My YPVS black box has a handwritten "GOOD" on the underside. It looks very good inside, too. I don't see the transistors in it that the 1984s had. Those were a replaceable problem. Anyway, it was replaced at some point.
Might use inline WAGO lever nuts for initial wiring.
Hoping to be able to visit, uhhh someone nearby, to have him load in his fave RZ curves into it before install.
the solder joints went bad ont he 84 boxes before anything else. the trick was a hose clamp and a bolt. it stressed the box and would make it work, ask how i know ;) sure we can load the curve in, but the one it comes with is good for sure.
I didn't know the Zeel was pre-loaded with anything useful.
John loads a stock program into his "1984" cdi box, which is not what I got.
I remember Tim saying your fave RZ curve made a significant difference.
Currently seeing the black/white wire for engine shut-off on the Zeel schematic and seeing the same color in the the original servo controller plug, (not cdi), wondering if it really wires into the Zeel.
the colors are different. when i did mine, i got a full vintage connections kit and made a harness to direct plug it in. im not sure where you got yours but i think they come pre loaded with an rz curve from borut.
Quote from: 1976RD400C on August 03, 2025, 05:58:07 AMhttps://www.economycycle.com/product-category/yamaha-rz-350/electrical/ignitions/zeeltronic-cdi-ignitions-controllers/accessories-zeeltronic-cdi-ignitions-controllers/
Thank you!
Quote from: m in sc on August 03, 2025, 07:06:30 PMthe colors are different. when i did mine, i got a full vintage connections kit and made a harness to direct plug it in. im not sure where you got yours but i think they come pre loaded with an rz curve from borut.
Mine came in from Economy Cycle. It has 5 programs in it, (but John isn't sure that a suitable YPVS program is inside). One curve mimics stock.
The #2 program looks good, but I'm not clear on how to set it yet. Maybe it defaults to stock and I ground the brown/green wire once to switch it to #2.
Gotta study some more.
^^ That's right, ground the wire for #2 ignition curve. I recently purchased the handheld programmer from Economy and you can change and monitor anything you want. Also, that new controller is going to "park" the power valve in the closed (low speed) position and I think the original leaves it in the open (high speed) position.
Got the cdi/YPVS control module from Economy. The Haase handheld was out on loan, so I wired it in anyway using Wago Levernuts after tinning all the ends and extending the stator pigtail.
It runs better. However, it's lean off the pilot and into the needle.
USB programming cable came in from Economy. Downloaded the RZ program and waded through the learning curve. Think I got it using Mark's curve plot points.
Raised the needles one step and turned in the air screws some.
Since it was raining and sweat was pouring from the heat/humidity, I didn't get to test.
Hoping for the best.
Happy to report that unplugging the thermosensor control and removing it didn't do anything bad. Made more room for the cdi pigtail.
Using the "velcro" cable ties was a necessity. Between them and the lever nuts, I can make changes, including adding shrink tubing later for protection.
there you go. sorry haven't been much help, been sick since Saturday and just useless. Got covid, pretty sure i picked it up at the hospital from my 6 mos lung scan. the irony :whatever: :huh:
Hospitals do suck. Spooky that we can all get a bug like that mid-summer.
Hope it's "just a cold" for you.
I expected to see what was already loaded on the unit and then tweak it, but the software doesn't work that way.
Appreciated the visit either way!
glad it's running better. if its now seeming lean, that confirms it was an ignition issue for a while.
yeah its more than a cold but im fine.
Stock RZ carbs are maybe sensitive?
Raised needles 1 step because it was lean there, and turned in air screws from 1.5 to 1 turn out.
Kid rode it and I listened. Told him to pull enrichener when it got messy.
Report is that it's actually a little rich in the needle range now, so back down 1/2 step is where I go next. Sounds kinda picky, but maybe that's a thing.
Should be going like stink all over the rpm range.
I'll work it out, but if anyone knows about those 26mm carbs being finicky on settings, let me know.
Thats why I put VM30s on mine and never looked back. I have both kinds of 26s. The infernal 48H EPA bridged style and a set of conventional 26s the rest of the civilized world got. I have very little experience with the individual non EPA 26s, but I assume they are like any other VM. The bridged carbs are a compromise at best on anything but a completely stock engine. Just my opinion. Your mileage may vary, etc. If I were building another stock or mildly mofified motor it would be flat slides, probably TM32 since I have one brand new one and a shit load of Mikuni brass. My 421 build has Keihin PWK35s on it and they are a whole different animal.
And I digress. Yes in my limited experience the bridged carbs are quite difficult to tune and after 1 time spending an hour trying to access the needles that was enough for me. I gave mine away to a dear friend.
I installed those UFO inserts on my stock carb slides and finally it runs great after spending hours trying to fuss with the needles. They said they fit an RZ but I had to open up the ID of the bottom of the slide to fit them in there. I have them in my VM34 carbs on my 400 and love these things. They make a world of difference, 0-1/2 throttle response is so clean and strong.
make sure the airjet is clear.
Thanks guys. I can formulate a plan now.
Mine are annoying because they seem to have a different slide stroke length. One has a larger gap at idle, but that same one is the last to completely arrive at wide open, slightly.
I have not checked the airjets yet, so there's that.
I have UFOs that should work, too.
They do work very well in the 400, though a little too small in diameter for those carbs.
At least it's down to carb tuning - except it's carb tuning on an RZ.
they are a huge pain in the ass. you might want to consider the pre jetted setup from toomey w the pwks.
Quote from: m in sc on August 29, 2025, 12:29:33 PMthey are a huge pain in the ass. you might want to consider the pre jetted setup from toomey w the pwks.
Shew, Mark. I can only do free stuff right now. Just had a little go at the hospital last week. We were at about the halfway point when a guy rolled up with his PC that showed $25k. Blew past the deductible well before that.
I'm gonna lay low and put in some serious garage time. I'll know how to pull, tweak and reinstall those stock carbs in my sleep. Went much smoother last time when I discovered that moving that electronics panel under the tank made the carb cables/adjustment a LOT easier.
oh I get it. trust me
Finally got jetted as good as it will go, dropping the needles 1/2 step from before.
Apparently the left cylinder is still not producing joy until it feels like it at higher rpm/main jet. Otherwise better than at the beginning of all of this, but certainly not right.
Last time apart, I did not "check the air jet".
Is there an embedded air jet behind a brass "ball" plug in the carb mouth of these unique-to-RZ VM26's?
Mark - I saw you mention to take the emulsion tubes out and put a carb cleaner straw in the air jet passageway and flush it out. Where does that come out the other side?
Can I remove a brass plug?
There are 3 holes in the carb mouth, one is open where the pilot air screws control flow, the other two holes are brass plugged.
Coil and 5k ohm caps are new. BE8S plugs are not, but presumed fresh and ok. They ohm out ok.
The only thing left is that the left carb must need help. The RZ seemingly bogs a lot on one cylinder trying to start off from a stop
Both needle jet tubes are clean - even the little mixing holes on both sides of the brass tubes.
Last desperate attempt will be to hope something is in the left carb air jet - wherever that is. Would love to actually get to get it out to inspect. This has been a major part of the problem all along, and never ironed out.
yup. carbs need a proper cleaning
How can I do surgery on that air jet and passageway, though?
theres a thread on removing the brass ball here somewhere in the tech section or chucks area
I thought that was only an RD400 thing and have done that to drill out the air jet for the much-needed Dave F mod.
Will do some research.
nope same thing. you can tap the housing and plug it back to keep the tune exactly the same after cleaning
Quote from: m in sc on September 04, 2025, 08:13:39 AMnope same thing. you can tap the housing and plug it back to keep the tune exactly the same after cleaning
Good news! Thanks much.
I have a couple extra carb bodies that I can experiment with :thumbs:
time allowing i can def help. I think an m4 or m5 set screw can be used to repugnant it, correctly, after its tapped. DO NOT re seal with jb wrld or a golf tee. ask how I know. (no i didn't do it)
Quote from: m in sc on September 04, 2025, 02:31:30 PMDO NOT re seal with jb weld or a golf tee. ask how I know. (no i didn't do it)
:eek: :dawg:
I'm just hoping to find the smoking gun, probably in the left carb.
Got the dingle ball out of the spare carb body. That orifice is quite small. Easy to see and clean. Pressed in brass jet, looks like.
Drives me nuts that I can't figure out where it's getting its air feed from. There's some 90 degree passageway coming in from absolutely nowhere before the orifice. If that is clogged there's no apparent way to get to it :tough:
Anyone know?
spray thru it see where it lands
i think its supposed to go back up to lines that go tot he stock airbox but i may be thinking of 400's
Found it in the extra carb body.
Yes, must have gone to the original air box through a tortuously routed passage and tubing.
I'm gonna cap that passage off and leave the air jet hole at the mouth open. Looking at the RZ as it sits right now, those holes are wide open to suck dirty air. It was traveling on some dusty roads before I got it.
Looking in that hole on the side, I was convinced it was a blind hole till I sprayed carb cleaner in and it and nothing sprayed back out.
I know that works on 400s and lcs, so should be fine on the rz. :like:
Quote from: m in sc on September 05, 2025, 10:43:30 AMI know that works on 400s and lcs, so should be fine on the rz. :like:
And I appreciate your take on that. Gives me a little more confidence.
Revised the photo. The feed for the air jet is also the bowl vent.
After some thought, I won't cap them externally, but try tying them together so the will be some "capacitance."
'Cuz I'm an expert :busey:
as lomg as they have access to atmosphere its fine
Clear now in both carbs. Hoping that is opposite of what the left side was, but once you drill through the brass ball, it's all a mess in there.
Quote from: m in sc on September 06, 2025, 10:42:02 PMas lomg as they have access to atmosphere its fine
And there's the question. Only real access to atmosphere is the pulsing racing air through the carb mouth. Not exactly quiet atmosphere.
Mikuni did make that available, but pounded a brass ball into it.
Am I overthinking?
Haven't gotten a chance to run it yet.
on the 400s they leave it open typically. worth a try. if it doesn't run right, thrn cap it.
Carbs never seemed to be the same and I'm going to have to go back in again.
Will verify the emulsion tubes are really the same and looking to drop the left needle at least 1/2 step lower than the right.
I'm still not there and now I'm going to try going rogue.
Left side still rich compared to right, air jets are wide open clear.
Fooling with air screws and about to go in to do silly things with the needles.
I can see the left ending up one full step lower than the right :umm:
That's not the way Mikunis are.
thats not right, that's a sign of an issue. lower fuel float level on the left carb by 2mm see if it clears
Took the carbies loose and twisted them so the float bowl could be removed and the float lowered. Ran a little better after that, but still not right - wet left plug and imbalanced.
Took them all the way out again and I had only accomplished 1mm lower on the float in the less than ideal twisted state. They were really both at the proper 21mm.
Sighted the carbs and saw they were not really lined up with each other, so loosened the joining brackets and realigned - doubting that will accomplish anything. Gave the left float another 1mm lower for a total of 2mm down. ALSO dropped the left needle 1/2 step, leaving the right one where it was. Maybe that will do it.
Really annoying that the slides do not agree with each other mechanically. I swear there is a difference in slide stroke from one side to the other. The only way that could happen is if the rotating lever in the carb top is longer on one side.
Buttoning it back up. Will ride soon. This has been a real mystery with the carbs having been dialed in really good at first.
Man what a hassle. I hate to suggest this, but you don't have a broken piston ring on the left side or something like that do you? My 75 350 had a broken ring on one side and it ran, but it was always a bit off and I think that side kept fouling plugs. That's what I remember from 45 years ago...
Compression has been really good, but haven't checked lately. Assuming that would indicate that sort of problem.
I'll check compression and try ripping around the neighborhood one more time. Just need to put the intake filter back on after last night.
Yeah I guess broken ring is a long shot, seems a compression test should show it. It's just so strange that there's not an obvious thing with a carb, only so many avenues to pursue there.
If you were made of money I guess it would be time to buy a set of aftermarket carbs and ditch the originals with the conjugal relations linkage/bracketry and the pain they are to remove.
I'm getting pretty good at removing, operating on, and reinstalling though.
(He says as his thoughts turn to forgetting an oil line hookup or some such disaster).
Quote from: 2steve on September 25, 2025, 08:34:40 AMI'm getting pretty good at removing, operating on, and reinstalling though.
(He says as his thoughts turn to forgetting an oil line hookup or some such disaster).
After the 5th time of taking my carbs off I ditched the throttle return cable. It's easier to get the carbs back on and it snaps back better.
all I have to say is: flatslides
Yep
Rode it during lunch with the lopsided settings mentioned above.
It's streetworthy now. Just a little disagreement-congestion at low throttle, lower rpm. Improves as it warms up. Not perfect, but at this point, riding it will take priority and can actually be fun.
Wondering how much of all this was the left carb.
Thread title should be "VM26 carb from outer space and whatever electrical issues combo platter"
def something wrong if carbs have to be staggered.
Your 2mm lower suggestion on the float was right on target though, along with dropping the needle 1/2 step more than the other one. Also opened that left air screw another 1/4.
It's art, not science :science:
Simple question(?)
Starts and idles great. Before it's warmed up, it acts like before; running on one cylinder at low throttle and lower rpm. Enrichener is on ONLY for start up. Yanking the "choke" doesn't change anything.
After warm up, it transforms to running normally.
After the ride-that-became-normal, both plugs are equally wet-ish around the circumference with a dry/normal electrode.
I can live with that, but shouldn't really have to. Wondering what gives?
To simplify the above, does the bike tend to lean out as it gets warmed up?
lean out or get richer feeling? is it actually dragging a cyl at idle? its hard to diagnose that w the crossover tube, i have plugs to isolate the intakes fir this very reason
Feeling rich. Starts and idles fine. Dragging a cylinder only under load at lower rpm when cold. Spooky when you have to pull out into traffic like that.
THEN, it all goes away after warm up and we're running normal.
After lowering the float level 2mm and dropping the needle 1/2 step, it got better and I'm almost home except for this.
Dropped both needles 1/2 step more. Left will probably remain down 1/2 step lower than right. That's what the plugs, feel and ears tell me.
Still better, but a sputtering thickness as the throttle opens under load. Annoying.
Rode it further than usual and after a romp through the gears, apparently the bowls get too dry and it slows down to let them fill back up. I'm blaming that on the TZR125 fuel valve.
It was nice to wring it out in 1st, shift to 2nd and feel the front wheel lose contact.
you're trying to tune out a fuel delivery issue?
Yes. Will have to get a higher volume petcock to make sure that there's no problem dropping enough fuel into the carbs. (Feeding fuel thru a "125" valve to a 350 might be a problem)
Then, drop both needles another 1/2 step. Trying to make small adjustments because there are only 250 miles on the rebuild which was running fine before these possible electrical issues.
and restrictive petcock . I think a raptor one works.
RD400 as stated earlier is cheaper and I think better.
I finally settled on a 1978 IT175 valve for my RZ. It has a large outlet and the original 1 into 2 hose setup can be used but you can't turn it on/off with gloves on.
That one looks like is has better reach coming down from the tank :thumbs:
Might not stick out through the hole in the side cover, but has a lever to grab.
I ordered a piece of crap from Amazon for $20 just to keep things moving but yours looks like a better move.
As Mark mentioned above a Raptor 660 petcock (5LP-24500-01-00) should work. You can even modify it to dual outlet if you want. Chuck (aka Supertune) did a write up about the mod many years ago on here.
raptor_petcock_5LP.jpg
raptor_petcock_dims.jpg
That's what I used on mine.
never had a feed issue even with bigger flatslides 0.02
Thanks, all of you!
You can see which of these will NOT have a fuel feed problem.
The needles are getting lifted to the point that I am wondering if another emulsion tube is needed. Gonna go another step - step and a half up and then investigate going up from 375 O-8 needle jet to whatever is next up in flow.
That is not obvious by looking at Jets R Us under VM26 round slides. There is no 375 anything.
Hoping for success before I run out of needle jet.
Gratuitous photo included, featuring the higher flow Yamaha fuel valve that has been suggested.
It seems the stock RZ carbs are one of a kind. I never found where you could get a 375 needle jet. They are a shorter length than a RD carb jet. Also the pilot jets are shorter length than other Mikuni pilot jets but you can find them.
those stock carbs suck.
man if nothing else get a set of pwks from toomey and ebay the stock carbs, somebody will want em.
Just rode it with needles as high as they can go plus a washer.
Seems like a needle shape/emulsion tube issue.
Mark, I don't recall your above idle iggy curve number, but maybe the stock carbs and internals can't deal with it.
Idle is fine, opened up above 4k is fine.
Part throttle and lower rpm brings some unhappiness. That's where the YPVS is supposed to be helping and there's sputtering instead of some grunt.
I was at the other side of the needle adjustment too and it was a bit little worse. It's just not there with this hardware.
I'll drop back and punt, hoping for a growth bonus from work for January 15th. Those carbs have been off and back on at least 10 times. I got good at it. That will help me for the rest of my life :busey:
just bring it to the house. I got my programmer back we can look at it one sunday if you want.
carbs dont suddenly need brass changes. :twocents:
Likely needed, as I can't figure it out and it would be foolish not to know and just get new carbs (when it's something stupid and unrelated that I might have done).
Speaking of new carbs:
Which PWK's from which Toomey?
28mm for stock porting and non-stock programmed curves?
They take oil lines?
etd has a setup for rzs, basically pre setup and ready to go. thats all I know
Rode today to prove that I could make it to your place, Mark.
Did well enough for that. No fuel flow issues anymore.
Clutch slips at max power delivery.
To me, that is actually good news.
Are FZ1 clutch frictions still the way to go on an RZ?
yup. good glad the fuel delivery is good.
IS clutch slip common on RZ's? Mine is 99% stock and I was wondering if I would need new plates in case I take it to the drag strip to get my brain back into gear.
Previously, the clutch was inspected, looked good, and assembled.
This is a fresh 2nd over 64.5mm rebuild. It was a cooler day and has a better ignition curve. Toomey pipes.
Seems that that combo of factors was too much. Seat of the pants said not much power delivery loss, but revved to 10k and stayed there while increasing speed.
Maybe it was right on the edge of being insufficient all along.
My clutch slips until the bike warms up all the way (15 minutes) and then it is ok. I've tried different plates, springs, oil but when cold it acts like an old Chevy power glide transmission when it hits peak power. It definitely stops slipping when hot.
fz clutch discs, fresh steels or blasted ones, and good springs should hold 75-80 hp easy. if not, somethings amiss
Carb set from Mr. Edmond at ETD is $700. Carb set with cable and fuel lines, no filter - bolt on and go.
He's a good communicator.
You know that sounds really good to me after spending all summer taking stock RZ carbs off and back on.
Still imagining that the left carb is dragging me down, (but it wasn't before) :huh:
Mark kindly blew his entire Sunday afternoon - on into some of the evening, earlier this week.
He went through everything that would be obvious, or not so obvious.
It's not the YPVS.
It's not the ignition controller. I probably still have a good original YPVS and 52Y ignig controllers.
Not the stator.
It's not the carbs. That took a good bit of time.
The "fuel feed problem" is not real. It's electrical somehow, related to the breaking up in lower range.
...and multiple other things were eliminated from the suspect list.
Good thing we went through and checked before I blew a wad of money on carbs.
I have the assignment to unplug the kill switch and do a ride test. That could be a culprit. Found out today that it is patched back into the system inside the headlight bucket.
Also - the iggy switch should be replaced as a precaution. $32 on eBay in USA.
Finally, the ride home being dark with one pull-over on the side of the road and then restart (weird, like the trip down on the interstate) revealed that the headlight is pointed too low and the turn signal cancelling is still a thing :thumbs:
So, I took encouragement from the signal cancel because I thought those all die after a few decades.
Thanks MUCH, Mark. At least he seemed to prove that I'm not an idiot doing something dumb.
It's no secret that he is a top drawer dude. It's also obvious that he and Angie are a match made in Heaven.
thanks Steve. it was fun.. but def frustrating. im glad we eliminated a bunch of things. you/we'll get it. as always, glas to help . and thanks for the kind words. yes, angie is def a special one.
I don't know M in SC, but it's awesome to see him helping everyone out with advice and/or hands on work. God bless you sir. This has got to be the most useful forum I've ever participated in.
Is there a specific rpm that you notice this is happening at?
Idles great. Trying to get it rolling from a stop is a problem. Above about 4k and over 1/8th throttle, it clears up. Constant droning away on the highway invites a slow decline to a possible shutdown pullover situation, but will start back up.
Above 4k and at full throttle is mostly a very pleasant experience.
its very strange. it -sounds- carb related but its def rpm related and came on suddenly. its so weird I used the 'batphone' and called Chuck Q. the carbs are def clean and sorted. its so strange. my opinion is its electrical. cdi/stator/coil all new and good.
Possible 12 volt power supply to the controller problem???
nope
Kill switch unplugged with the the hot end safely encapsulated in the headlight bucket. New ignig switch is in.
But the eagle hasn't landed. To be fair, I want to get the needles back to mid position and try it again to see where it "really" is.
The test will always be to take it out to drone away on a big highway to see if I have to pull over on the shoulder.
Had noticed on the way home from RHill that it would start to lose power, then I'd flip the kill switch and just before it died it would give me a couple strong beats first :umm:
Could it be a wiring/conector issue? I'm thinking 40 year old harness could have a conductor that ohms out ok, but can't carry an amperage load. Do you have a way to load test wires?
could be in the harness. I find it unlikely its the needles but .... its a really odd one for sure
I'll try a fresh fat black coil ground wire, then a fresh orange coil wire* along with centering up the needles. Can't think of any more influential wires than those since stator and stator wiring were replaced with no change in performance.
Just ordered some more goodies from Yambits, so there's still optimism inside.
*Both look OK and ohm out at zero. Strangely, there's an extra unused old orange wire next to the actual black coil wire but the other end goes nowhere.
Quote from: 2steve on November 22, 2025, 07:31:37 PMI'll try a fresh fat black coil ground wire, then a fresh orange coil wire* along with centering up the needles. Can't think of any more influential wires than those since stator and stator wiring were replaced with no change in performance.
Just ordered some more goodies from Yambits, so there's still optimism inside.
*Both look OK and ohm out at zero. Strangely, there's an extra unused old orange wire next to the actual black coil wire but the other end goes nowhere.
If you are trying to establish there is direct point to point continuity of a single wire, I believe it should read something like ~.1 to 10 OHM depending on wire gauge. If you read nothing (0 OHMS) point to point it means open circuit. Just curious if your meter is Analog or digital? Also, if you have different ranges you are able to select for reading sensitivity.
i think its in the harness somewhere. the fact that it idles well, then runs like absolute ass from 2500-7 k, then cleans up, regardless of throttle position, seems electrical. also that 1: it came on out of nowhere out of the blue one day,2 the carbs are super clean, 3: over 7-8 k it runs awesome.
it feels like its 'leaking' high voltage somewhere. the odd part is that it cleans up high in the revs.
and the pvs are working correctly as well.
IF you get a 2 carb split cable setup, we can put a set of individual ones i have for testing on. i dont have a setup for that (cable wise).
Would the magnetism on the flywheel be letting me down?
Otherwise, I can't find where high voltage might escape in the wiring diagram. That coil is new, but didn't change anything.
Maybe I track the kill switch path on the other side of the new iggy switch.
Red/white wire from the kill side.
....
no,weak magnet will show itself at lower rpm typically. and, I've never seen that on sn rz tbh.
the harness does carry voltage from the ignition. im not q00% sayi g thats it, but aside from the coil being g only id be looking at the harness next
My experiance with stock carbs: They acted up right between 5-6000 and that was it. Starting, pulling away from a stop, no stalling, and everything that wasn't in that rpm range was normal. You could watch the tach and say "ready, right now" as it hit 5000.
"If you are trying to establish there is direct point to point continuity of a single wire, I believe it should read something like ~.1 to 10 OHM depending on wire gauge. If you read nothing (0 OHMS) point to point it means open circuit. Just curious if your meter is Analog or digital? Also, if you have different ranges you are able to select for reading sensitivity."
I have to differ. The opposite of zero resistance is infinite resistance. If you short the leads of a multimeter together your meter will display zero resistance.
Quote from: 1976RD400C on November 23, 2025, 10:34:51 AMMy experiance with stock carbs: They acted up right between 5-6000 and that was it. Starting, pulling away from a stop, no stalling, and everything that wasn't in that rpm range was normal. You could watch the tach and say "ready, right now" as it hit 5000.
I had this as well a couple of years ago with my original set of carbs, and believe it was caused by worn needles and/or needle jets.
guys, when this thing goes into bog mode, it feel like its goign to just stall and die.
And when going 60 mph steady speed, I have to plan to pull over safely as sometimes, unpredictably, it will slowly wind down to a stop. After stop, it will kick back to life like nothing happened.
Like something got too hot?
not a heat issue.
Looking at the Zeel wiring, I only see +12 vdc and the wires to the coil that could be suspicious since they are still embedded in the harness. Everything else has been changed out with the same symptoms as a result.
yup. look there.
OR, bypass them and make new ones.
Seems like if it isn't fuel starving it has to be heat or something that breaks down with current (amp) load.
it does it from dead cold startup as well. like said, confounding.
Seems like the continuous 55 to 70 mph speed just kills it off somehow. At that time, with the 15t front sprocket, the RPMs are up in a "good" range. Maybe wiring getting too hot from load and going open or increasing resistance. I dunno.
Yeah Matt, feels just like the bowls go empty but Mark would add that the bowls going empty would make the bike lurch on its way out. With this RZ, it just winds down smoothly to only low rpm or altogether cut off. Got a higher flow petcock on now, for sure.
I rewired the coil ground straight to the battery terminal and the the other coil wire straight to the orange coil wire from the Zeel. Checked the + wire to the Zeel from the fuses and there's no smoking gun. Changed the fuse, just in case. Fuses get weird sometimes. Haven't gotten to try it out yet.
Yambits came in today - 3 days I think. FedEx - NO TARIFF surcharge on $260. I'm even happier about the genuine Yambits sticker I found inside one of the parts boxes.
I'm somewhat confused and possibly a bit stupid. Isn't that the power valve controller in the center of the picture? Do you have a Zeel controller (VCDI10VT)? Why are you using the oem power valve controller? :umm:
no the originsl powervalve controller isn't being used and its not on the boke
Quote from: 1976RD400C on November 24, 2025, 04:21:49 PMI'm somewhat confused and possibly a bit stupid. Isn't that the power valve controller in the center of the picture? Do you have a Zeel controller (VCDI10VT)? Why are you using the oem power valve controller? :umm:
The original power valve controller was still good (located much further back when it was previously in). Yes, that PV control is also built into the Zeel I got from John at Economy Cycle. He very conveniently had it in stock. That black cube in the photo is, uh... I don't know. Red and black wires are the new overly fat coil wires. The new coil from Yambits with the "H" on it didn't help.
we verified PV operation as well. its good.
The black cube in the photo modulates flatulence output. And at least you got a Yambits sticker to aid in the happiness of this RZ journey that began in Michigan.
I just read back through the whole thread. Before I did that I was thinking filler cap not breathing, but I got back to the first page and it looks like the same problem is still there after all sorts of changes.
If that is right, then what changed since it ran right, or maybe it never ran right since it was built. If it ever ran properly then the question is what changed. In either scenario I would start by borrowing a different set of pipes and see if that eliminates the issue.
It does sound like incomplete combustion above idle and below say 4,000 which may be an adverse pipe resonance effect. I don't have any dimensions for the #375 needle jet, so I have nothing to recommend as a possible alternate, but I suspect they are like #284 on late model RD400 which were an air bleed type but with the tall discharge nozzle.
it ran perfect, nothing was changed.tgis was also on a fairly fresh motor. it came on suddenly. therein lies the rub.
Side stand control unit??? That is electronic with a scr in it and is connected to the engine kill circuit. Maybe try disconnecting it. :umm:
Any chance you have access to another wiring harness? Swapnostics is a valid technique!
Quote from: m in sc on November 25, 2025, 12:07:58 PMit ran perfect, nothing was changed.tgis was also on a fairly fresh motor. it came on suddenly. therein lies the rub.
Just so I understand it, the bike ran fine after the motor was rebuilt and then suddenly had this mid range issue? Or was it broken in and the problem wasn't identified until it was run harder?
Quote from: m in sc on November 25, 2025, 12:07:58 PMit ran perfect, nothing was changed.tgis was also on a fairly fresh motor. it came on suddenly. therein lies the rub.
Just so I understand it, the bike ran fine after the motor was rebuilt and then suddenly had this mid range issue? Or was it broken in and the problem wasn't identified until it was run harder?
had mileage on the rebuild then came out of nowhere is what Steve told me..
I can imagine how frustrating this has been for you both. It's a really odd to have a problem suddenly appear out of nowhere and for it to only impact above 4000 and idle. If it were fuel starvation it should get worse as revs rise. If it's a broken or shorting lead somewhere it would normally get worse as revs and vibration increase.
We tend to gradually open the throttle so it's hard to isolate rising revs from rising throttle effects. Is there any difference at those problematic revs for example with small throttle openings compared to banging it wide open? with the zeel, it might be an idea to try it with PV closed via software compared to wide open compared to partial throttle.
Just thinking out loud here but is it possible to see Zeeltronic conditions as it runs say on a dyno or does someone have a datalogger that they would lend to the cause to track mixture, revs, and Throttle position to see if that data sheds light on where to look?
Fuel should not be an issue because if it's bad it usually causes problems all through the rev range.
Another thought: might be an idea to go back to stock carb settings and ignition and PV timing and then swap out the pipes for a different set. If no change then the pipes are not related though they may exacerbate the issues.
the zeel was put on to combat this problem. its not the zeel.
the carb settings were proven for years prior, its a toomey setup on the stock carbs.
the stator was rewound by my suggestion due to a very similar issue we saw on another RZ. thats not it.
the coil was swapped to combat this. same.
I used the batphone and called quenzler directly, he was stumped as well.
so, by process of elimination, if it were MY BIKE, id rewire the ignition or replace the harness. to be honest, id actually bypass all of it, test it directly wired, then slowly add systems back.
I'll be honest, ive never really felt anything quite like the issue this has. steve explained it to me, i test rode it and was completely baffled, and ive seen some (And caused) strange shit. this one has me stumped aside from what needs to be tested next in the wiring. I'm not being stubborn, but theres been a lot of process of elimination.
The latest wiring bypasses, coil ground and coil orange wire have been run direct. Brown positive from fuse box inspected and ohm'd. Looks fine. Checked other browns coming out of the fuse box. They are solidly soldered together as the schematic dictates. As of today, it still runs the same.
I only see that I could trace the brown wire that goes to the regulator/rectifier and the ignition switch plug to either bypass or look for a smoking gun (iggy switch being new now).
Should I replace the reg/rectifier so as to continue this journey of great success?
Otherwise, yes, buy a harness and start working it in. The bike will do its retarded stumbling at the lower rpm, then I open the throttle wide open out of spite and it will start to catch, pop and falter back into its abysmal malaise. Really did run well previously. Then I parked it one day and rode it later to find this issue.
The entire ignition system is self-isolated because of replaced parts except for that brown wire pathway to the regulator - to the best of my knowledge. Rick's stator said my original tested good and I probably have a good removed YPVS box and 52Y CDI box.
Hoping the regulator/rectifier would be the prob. That would affect voltage to the Zeel, among other things.
Since I was in the headlight bucket and feeding a new ignition switch plug in, I put my spare Auxito LED bulb in the headlight. The YPVS cycling is faster now without the halogen bulb sucking down the voltage when you turn on the key. Still no improvement, though.
Teazer, I feel bad that you wasted so much time that you will never get back by reading the whole thread.
It really ran well before this and when even when it hits the pipes now, it's just fantastic.
the rr would have had zero effect on the stock cdi box which had this issue too, so, thats not it either.
I realize that the two of you have been thorough and approached this systematically. I'm just trying to look at it with a fresh pair of eyes to see if there's something I might have tried.
Regulator rectifier is unlikely to be the problem, but you could disconnect the whole charging system and run it around the block as a total loss. That would at least eliminate one more variable.
If it is indeed electrical is it possible that there is RF noise from some source that is creating a problem at certain revs/frequencies? We have a bike on the dyno that hit 6500 and it felt like it was hitting the rev limiter and with that heavy dyno drum driving things it was pretty violent and the deto counter was flashing like a cop car. The only thing that could have caused it was RF noise from the dyno or the charging system.
The fix was a length of stainless steel braided tube from the hardware store to shield the pickup. That was an Ignitech system with new pickup not an OEM pickup like the RZ, but you could try wrapping the pickup leads in foil just to test it.
With the Zeel software, can you monitor what it's doing? If so, you might be able to run the bike on the center stand and run it in gear up to say 4k and see if anything stutters or changes in ways that are unexpected. But the symptoms were there with stock ECU, so that's unlikely but you are looking for something unexpected.
its not it, i know that fault(had it with a very early mzb and zeel years ago) and it has a different feel. (more of a stutter) this just goes flat. it very much -feels- like a fuel situation, but it does it at varying throttle positions, thats the 1st thing I tried when I rode it.
Correct. That is more of a stutter as if someone was flicking the on-off switch very quickly. I sense your frustration there.
Is there a dyno close by? Run it with sniffers in the pipes and watch to see if anything goes out of whack as it runs. Or borrow a data logger and fit an O2 bung and log revs against A:F and look for anomalies. It's hard to read that data on a 2 stroke but might reveal something.
As the anomaly doesn't appear to relate to throttle position, it is more likely to be electrical.
I'm turning over thoughts of trying resistor plugs along with the resistor caps already in place.
Also, the foil thing on pickup wires, though the prob was was previous to the Zeel and stator replacements. Rick's Stator put a new glossy black sheath over most of those pick up wires.
None of that agrees with, "It was running fine when parked, and the next run was a disaster."
However, going through to eliminate sometimes forces a discovery.
Quote from: mnein on November 25, 2025, 09:26:39 AMThe black cube in the photo modulates flatulence output.
Having snooped a little in internet photos, it looks like it's the sidestand control unit. That runs down into a shared plug to the stator and neutral switch.
It is, after all, hard to flatulate whilst sitting on a motorcycle seat.
The green pickup wire goes direct (and already did) to the Zeel unit without disappearing into the harness somewhere. I was hoping I'd find something there.
Wondering if there's such a thing as RF getting introduced into the ignition system by way of harness proximity to the new spark plug wires, thick rubber covering and all.
Next move would be a chat with John at Economy for a complete harness to patch in or stainless braided sheath.
not rf
The only engine ground I can see is the black wire off the stator.
Should there be another or an additional one to put in place for the RZ?
I usually run a redundant ground, won't hurt
A video of how it runs may help :umm:
Geez, 16 pages of PV or something flatlining the thing.
Maybe I read the whole post and weed out muffler bearings.
cliff
Yeah, don't read the whole thing. Time is too precious. You won't get it back.
Maybe read the 1st post and then know that the stator and control electronics are all new now, carbs & YPVS checked out good but it's still exactly the same.
Time to waste, I am retired.
I have read the whole thing.
I have H1's and a DT250.
I am not privy to the RZ bikes as to how the exhaust is mounted to the Jugs.
Nor am I knowing the exhaust system, is it US or CAN? Paint suggests CAN with zero cats.
Crank seal leak-down done? both left/right and l/r to each other?
c
has nothing to do w any of that. its a basic rz setup w aftermarket pipes. motor is fresh. it idles perfect and runs up high perfect. this rules out:
crank seals
reeds
air leaks
worn rings
etc.
its all midrange. we verified the pv position and operation.
it -feels- like carburetor but it did it to me at 1/4 throttle And wide open. it follows rpm only.
rpm specific issues regardless of throttle position point towards electrical.
as does the fact that it ran fine, then suddenly just didn't. after the motorvwas refreshed, and had some mileage on it.
if it was MY bike, id get a set of individual carbs and a splitter type cable to eliminate the stock carbs . and.. honestly, they work better.
its a us model fwiw.
I'm with you, Mark. Just one thing blocking me - besides the dollars: I would be hating life if I got new carbs, or a splitter cable so you could help, and then find out that's not the problem. Thus possible wasting your time (again). If someone has a loaner set of known good RZ stockers, that might be a thing as well.
Still haunted by the possibility that the on-highway random shut downs are related to this problem and it's not lack of fuel feed. There's a teachable moment there, but I'm a retarded student.
Gonna run an extra ground pipeline today and I have determined that the original coil mount that I copied with the new one was needing to be turned. I have no hope that this will change anything. Just makes me feel better :busey:
Thank you for hanging in with this thread, Automan. The pipes are Toomeys and were the bomb back in the day. Finding an RZ with factory pipes is not very desirable and it would also be very rare.
I have individual carbs we can test with if you had the cable setup. I don't think that's it but it eliminates a possible cause. we're down to elimination.
its not a bother, I offered. if I don't want to do it, I won't :Clown:
It
Quote from: m in sc on December 05, 2025, 02:48:34 PMhas nothing to do w any of that. its a basic rz setup w aftermarket pipes. motor is fresh. it idles perfect and runs up high perfect. this rules out:
crank seals
reeds
air leaks
worn rings
etc.
its all midrange. we verified the pv position and operation.
it -feels- like carburetor but it did it to me at 1/4 throttle And wide open. it follows rpm only.
rpm specific issues regardless of throttle position point towards electrical.
as does the fact that it ran fine, then suddenly just didn't. after the motorvwas refreshed, and had some mileage on it.
if it was MY bike, id get a set of individual carbs and a splitter type cable to eliminate the stock carbs . and.. honestly, they work better.
its a us model fwiw.
So why chase carburation?
How about collapsed baffle(s) in aftermarket pipe(s)
Pipes that were good suddenly flat regardless of throttle sounds like pipes out of tune with engine.
i.e. Factory Pipe Product on my H1 has the flatspot at 5-5800rpm regardless of throttle.
They are tuned for 9200. They have zero baffles. Stock exhaust no flatspot.
cliff
if it was a collapsed baffle it wouldn't rev high. i had one in an FPP kill a piston years ago. i get it.
Not chasing carbs, i feel its electrical. Process of elimination, though, has its value here as well. Ive never had one do this, and i thought i had it sussed till i rode it, i've honestly never felt one do quite what this is doing. Hence why i reached out to chuck q.
gotcha
cliff
We may have covered this a few pages back, but have you tried swapping a different set of pipes - just to see if the problem goes away? If you were closer, I would offer my RZ350 as a test mule for swapping parts. IS there anyone closer with an RZ that you can borrow parts off to do back to back testing of swapped parts?
that makes no sense as they worked fine before. theres no collapsed baffle so..?
Can we review the carb set up? Stock needle jets and needles? Stock pilot? Does the needle jet seem to fit in the carb body ok? Does the main jet and washer fit ok with a snug fit to the needle jet and carb body?
all is good there,I went thru them myself as well, and they were fine. I was hoping for a smoking gun there, nope. had a toomey kit as far as I know. I was looking for clogged air jets, etc, none of that. :huh:
Toomey pipes and Toomey jetting. Really ran fine until about May.
I am not familiar with Toomey, but do they have internal baffle(s)?
Wirges for Kaw H1's were notorious for breaking baffles and flopping around at different positions at certain RPM's.
This is why I ask.
cliff
oh, no nothing like the wirges 'washer'. im very familiar w those. these,are straight thru. like dencos.
Quote from: 2steve on December 09, 2025, 12:49:04 PMReally ran fine until about May.
What changes, mods, or maintenance was done in the time immediately preceding this?
Quote from: m in sc on December 09, 2025, 02:53:57 PMoh, no nothing like the wirges 'washer'. im very familiar w those. these,are straight thru. like dencos.
Ok, scratch that.
Thanx!
Going back to the first post in May, one needle was replaced and the tank was sealed. Did either of you check the needle dimensions and compare those to stock or the the needle that wasn't changed (or the one that was)?
I did measure them to compare with higher quality calipers.
They were really close to each other at the tip, midway and near the top, plus overall length.
That still doesn't explain why I'm running the highway or interstate in the good rpm range and it slowly winds down to a crawl or completely stops
If it does come to a stop, it will kick back to life like nothing happened. This behavior started the bowls-running-dry theory that has been disproven and appears electrical in nature.
How about trying to gap the plugs smaller and then see if that changes or stops the highway slow down problem?
Since the initial problem, plugs have been changed twice. Mark popped in some B9's and then I've tried B9EIX. These have been pre-gapped according to the middle of the RD400 range. Haven't tried to narrow the gap.
Every time the highway failure has happened, it has been very sketchy. No shoulder/busy road at night or interstate with orange barrels narrowing the the shoulder. It's hard to be excited about trying that out again.
I gapped the ones i put in at like .025" or so.
If you are at your wits end :bang: and still think it could be carbs I can let you try my stock carbs as long as you treat them like a newborn baby, don't alter them in any way, and promise me I get them back right away with insurance on the package. They work good, real good. :clint:
I might take you up on that. But still trying to find an electrical smoking gun because of the shut down situation.
Correctly repositioned the new coil, in process of running another ground, etc.
Thanks!
my 0.02. id definitely try it to rule it out as a possibility. if none of that works it reconsider a new harness (and use correct Japanese style connectors )
Just like dr. house
Quote from: automan on December 11, 2025, 12:33:52 PMJust like dr. house
Yessir! Exactly. Been thinking just that for quite awhile now.
I'm still waiting for someone to make that offhand comment that turns the light bulb on and I grab the cane and limp to the garage to fix it.
Usually happens within 45 minutes on a House episode. So far, nobody is calling me an ass yet.
I wish it was like an episode of house. we would have been done in an hour then had time for donuts 🍩 😅
Quote from: 2steve on December 09, 2025, 07:31:58 PMI did measure them to compare with higher quality calipers.
They were really close to each other at the tip, midway and near the top, plus overall length.
That still doesn't explain why I'm running the highway or interstate in the good rpm range and it slowly winds down to a crawl or completely stops
If it does come to a stop, it will kick back to life like nothing happened. This behavior started the bowls-running-dry theory that has been disproven and appears electrical in nature.
That particular symptom sounds exactly like a partially blocked air vent in the filler cap. Bowls run dry and when the bike stops, enough air gets in to allow fuel to flow.
yep, I thought vapor lock too, and it's easy enough to check (on dirt bikes at least) by removing rubber gasket and locating breather hole in the cap and blowing compressed air through it. Had a couple plugged holes in my lifetime. Only other thing that mimics the "runs for a while, shuts down, and starts up easily again" is an ignition coil that goes open circuit winding when hot, but cools down, closes the circuit and starts again. Mark has tons more experience in this stuff than me so I expect he'll solve it soon enough.
that too has been tested, i thought the same thing.
There is a brand new coil on it. Had never taken it for a long enough ride with the old coil to compare the shut down symptom. So, there's that.
https://www.economycycle.com/product/1984-1985-rz350-usa-wiring-harness-48h-82590-50-00-reproduction-harness/ (https://www.economycycle.com/product/1984-1985-rz350-usa-wiring-harness-48h-82590-50-00-reproduction-harness/)
I am generally critical of firing the parts cannon at a problem, but $150 to replace 40 year-old wiring seems like a reasonable step. I surely have an extra harness you could borrow for testing, but once you've paid to ship it across the country twice and gone to the trouble of swapping it out, you could have supple new wires and clean connections and eliminated a possible cause.
I agree, Wade.
And maybe the new coil is part of the problem(s). I have the original to try out on the highway. Separate issue?
John has a plug kit for the aftermarket Zeel to plug into the original harness. So that, along with his harness, is a serious consideration that I'll likely go with.
Then there is the offer from Mark and Marc to help with carbs.
I'll be working thru it all in the usual throw everything at it so when it runs right, I don't know exactly why.
The parts cannon has been a problem so far, and it usually is.
Still thinking about the previous reminder that I changed a rough looking needle to a new Toomey. The reason was because the carbs wouldn't act like they were synch'd but not because it wouldn't really run well. That was probably the left side float difference.
I thought you were to put it back to stock, or when it ran good then go from there?
It was stock, other than Toomeys with Toomey jetting. Any changes that were made were to overcome the new poor low rpm running problem.
The new Toomey replacement needle could be suspect and the new Yambits coil could be suspect of the other possibly-newer separate problem.
It's still a mystery and now it's harder to cuddle up with it in the garage and test ride.
Last I looked at the carbs after the visit with Mark, (using his correct point of view to check from the cylinder side instead of the filter side), the right carb really is different in slide stroke. Changed it to be equal to the left at lift off. Now wide open is unmatched.
Didn't fix it down low though.
we checked it.. they are even . but this is the last thing that was touched, hence why id like to eliminate it as a possibility
While you are loading up the parts cannon, I wasn't sure if it dies suddenly like hitting the kill switch or it just sort of dies away like running out of fuel. The first suggests an electrical issue and the latter, fueling. And IIRC, there was an issue at part throttle/low to mid revs that clear up at higher revs. That would suggest PV timing, pipe resonance or needle portion of the fuel map. If it feels more like it is tightening up and then frees up it could be too much advance at those revs.
Just thinking out loud again, which is always dangerous.
It smoothly ramps down on power, leaving time to find a place to either pull over or let off the throttle hoping that it will come back some before it completely dies. First time, I was sure it must be seizing. Crapped my pants.
It does not lurch like it's running out of fuel. Mark did a flow test on the tank/cap/petcock and the needles+seats are new.
I somewhat suspect the new Yambits RZ350 coil on this. There will be testing with that against the old coil - which was probably working just fine but became a victim of the parts cannon BEFORE this highway die-out situation came to light.
Also, I have switched from the new Toomey needle to the old, chewed up Toomey needle - mentioned in the very first post - and you pointed that out, teazer.
Figured out how to change the needle without removing the carbs. Fiddly but can be done.
Test ride is pending on that. Maybe Sunday with the 64 degree F high.
I'm not confident. Hopeful though.
holding the throttle when i rode it at 1/4 , 1/2 and 3/4-wide open yielded the same results (flat almost dying ) , between like 3k and 7 k, then it takes off. mind you i didn't ride it much but it was VERY VERY noticeable .
Loose or cracked reed?
broken intake skirt?
steve said the reeds were good, intakes looked great
Not that I'm an expert, but that thing just delightfully rips above around 7k rpm. So much so that the clutch has started slipping - and that clutch slipping didn't impede acceleration either :eek:
Surely that can't happen with any type of reed problem.
So much stronger than I recall with the fresh '84 RZ that I used to own. It's at 64.5 mm bore.
Also, as I stated to mnein when he asked for a comparison, there is definitely more area under the HP/Torque curves with an RZ compared to the RD400, (both stock with pipes).
OK. I thought that is was dying out like a flat battery or fuel, but that sounds more like a pipe effect. At a steady say 35mph in 5th or 6th, just curing along, if I open the throttle all I get is intake noise as it slows down. Drop a gear or three to get the revs up and it sings, but at lower revs, no amount ( little or large) of throttle makes much difference, except to intake noise.
I have an older pair of Spec2 pipes on mine and as long as revs are high enough, it is very responsive.
if you could borrow a different set op pipes to do a back to back comparison, that might shed light on things.
why would the pipes suddenly stop working? its not the pipes. the baffles are intact.
I took it for a spin today. Since teazer mentioned my first post saying I had just changed the needle, it only made sense to change it back. Took the pristine new Toomey needle out of the left carb and put in the chewed-up old one. Turned the coil around, (not flipped, but turned 180 degrees to correct orientation - shouldn't have mattered), and had run a ground from a couple places on the engine to the battery negative and frame with a 4 connection ground wire "harness".
All that to say that the needle change is indicating that the left carb is the issue.
It really does pull through the lower rpm better now but reminds me of why I changed the needle in the first place back in May. Moves more boldly into traffic and is more usable at low throttle.
Will run it again later this week as we are supposed to approach 70 degrees but I feel there might be evidence to convict the left carb in a court of law. Will get it out more on the open road to check what I presume is/was an issue with the new coil.
The new coil wouldn't install the other way because the harness plug wouldn't reach, but since I lengthened the harness with direct wiring, it allowed the orientation that eliminated the ridiculous bends in the spark plug wires.
We'll see. I got my 30-year reward gift card from work, so that will help toward new carbs.
Still can't point to a detail that could be called a smoking gun after all of this. That old left carb that doesn't match with the right likes its old chewed up needle. Meanwhile it's spoiling the show.
Would be a dream come true to have it running great on the road for Spring.
PWK28s, one way or the other.
This is how I fixed my RZ stock carbs. It's kind of astonishing how they transform how it runs. I have them on my 34mm RD400 carbs also. I was skeptical at first but found out, wow.
https://www.economycycle.com/product/ufo-ultimate-flow-optimizer-for-rds-and-rzs/
I have those on my RD400. Had to fiddle with them because the fit wasn't spot on. They work very well. Pilot size goes WAY down and they make it crisp.
That left RZ carb though, it's not something I want to pour more effort into. Something is wrong with it that just isn't obvious.
Planning to look at the PWK options out there at this time. Can go the DIY route and save a few hundred or Ed Toomey complete kit for $700.
Still appreciate your carb loan offer and UFOs are def good advice.
So much for putting it back to stock.......................... :dead:
:umm:
If it runs better with the old bent needle than it did with a nice shiny new needle, which seems to defy logic - Unless there is a matching problem with the corresponding needle jet. Ebay Australia has a Keyster replacement and CSMNL look like they have stock ones.
Might be worth popping them both out and checking the orifice to see if there are signs of gouging or interference on the bad side. If the bent needle has created a larger that spec needle jet orifice, that would create a rich fuel situation causing it to bog down.
Quote from: teazer on December 22, 2025, 03:23:57 PMIf it runs better with the old bent needle than it did with a nice shiny new needle, which seems to defy logic - Unless there is a matching problem with the corresponding needle jet. Ebay Australia has a Keyster replacement and CSMNL look like they have stock ones.
Might be worth popping them both out and checking the orifice to see if there are signs of gouging or interference on the bad side. If the bent needle has created a larger that spec needle jet orifice, that would create a rich fuel situation causing it to bog down.
I had this issue a couple of years ago with my RZ. My symptom was a bog at a very specific and very small throttle opening; 6th gear and just under 1/4 throttle was the worst. It was worn needle jets and needles. When the grooves worn into the needles aligned with the top of the needle jets it became rich and started losing RPM. More throttle or less would get me out of the flat spot.
I'm going to drop back and punt the both of them. Wasted too much time this year trying to coax them into working better. Not getting that time back and I became an expert at removing stock carbs. Not really a coveted life skill.
For some reason these bikes are really tricky to get running just right once the original pipes and air box come off. :bang:
I've never had an issue tuning an rz. tbh, none have been stock, either. those stock us carbs imho are garbage. you can get better performance running Dave f modded 73-75 rd vm28s with a y boot on an rz all day long.
I concur with Mark. The stock carbs are junk.
Quote from: Kawtriplefreak on December 23, 2025, 10:50:19 AMI concur with Mark. The stock carbs are junk.
And I'm jumping right in on that.
Nobody wants RZ stock pipes. Experience has added stock carbs as well.
On the other hand, the RD400 is running crisp, responsive and quick today at 67 degrees.
Yay DaveF VM28's with fudged in UFOs and ChuckQ "update" porting with FPPs.
Extended test ride today in 77 degrees F. Still more manageable with the gnarly needle, (it's not bent, just "chewed").
That still points me to new carbs.
However, riding 21 toward Rock Hill I noticed that going downhill and pulling in the clutch, the engine would stop. Obviously, I had felt the need to do that.
Turned around to go back and it stopped under power. Pulled over, had to turn off the key, then restarted.
I'm gonna change out the new Yambits coil to the original RZ one that I thankfully kept. It's ugly, but might just work better.
:umm:
I am concerned about my dual outlet RD400 petcock flowing enough fuel to feed the PWK 35s on the 421. So I will be ordering the 660 Raptor petcock and modifying it for dual outlet. I considered a Pingel but I want to keep a reserve feature and am also worried that the lever on the petcock won't clear the RZ side cover.
If it's really the carbs, and it could be, I might have a fuel feed problem after all. Last time I had it out, it was lurching some when slowly dying on the open road.
My petcock flow passage (recommended by Mark) looks generous, but I also bought a genuine RZ unit with plans to put in a second outlet. Besides that, I would be able to turn it to reserve while riding under duress.
Wondering too about bowl filling inside the carbs through the needles and seats.
These ponderings would go better if Chuck Q were to jump in. Your concerns especially.
not petcock issue
I see genuine PWK 28's on eBay that must have come from Sudco - new in box.
Are any of those ok for the RZ, or do they have to be a certain part number?
Assuming they are not drilled/tapped for an oil passage which could be added later.
dont assume. even the knockoffs are ok though.
you need a jjh needle, roughly a 142 main150 and a 38-42 pilot should be damn close. or just try a set of vm28s
$100 each for genuine and $30 for knockoffs painted black with red highlights.
I'm okay with $30, but life lessons make me a little nervous about getting 2 actual good carbs at that price.
Not gonna argue if there is assurance that they are fine.
some knockoff are good. some aren't . just depends. keep in mind the y boot will no longer fit, you need to deal with cables, etc. did you get the coil swapped etc?
Coil swapped but had a stoppage. Didn't have enough evidence to blame on the swapped coil. Could have been low fuel in the tank and couldn't reach in that RZ side cover hole to change to reserve while underway. It did lurch a little as it was dying out.
Figuring best to go with carbs next.
Economy for throttle cable, I see.
I need to get angled adjusters(?)
And you are offering printed Y boots that would work?
.. no im not . get unis but honestly, get the ign test sorted. if you want we can throw some vm28s on to test before spending the money on carbs. just need the cable
this may have been covered already in the past 19 pages... but has the top end ever been off this motor?
yes. it was rebuilt, ran great for a while, then this suddenly came put of nowhere
Quote from: m in sc on January 29, 2026, 04:02:32 PMyes. it was rebuilt, ran great for a while, then this suddenly came put of nowhere
There's about 300 miles on a very well rebuilt engine with new Yamaha crank. mnein did it right.
I hear you Mark. Will work on acquiring the cable set up.
Maybe even steal the still-fresh VMs off the 7,700 mile RD400 in the garage.
not a bad idea. Will be good for a test
29L2626000P: CABLE ASSY, THROTTLE & PUMP (NON O.E. ALTERNATIVE) Yamaha - buy the 29L-26260-00P at CMSNL https://share.google/mPX8Pwz6VFQaW3cNQ
Got it. Thanks!
And the Norway only country choice just gave way to include USA, so it's on order.
Any updates?
Removed the stock RZ throttle cables and installed the recommended split one from CMSNL. Next step is swapping the RD400 carbs in.
Maybe there's a part that will get me from the RD400 carb top to the new split cable end?
The long straight hex does not come off and the plastic liner sticking out won't budge.
Looks like a 45° would be good with male threads at both ends.
Niche cycle
Mikuni VM TM Style Carburetor Angled Top Cable Elbow Adjuster I-M22-10-3 | eBay https://share.google/NfVVEKDspZwyVuujp
On order. Thanks, Tim!
So...?
The 45° carb cable adaptors are in.
The cable ends won't start to fit through though.
I'll do a compacting roll on the ends this weekend in some improvised way to get the diameter down. Should work after that.
Other things going on. Dryer needed new parts and there are grandkids. I'm slow. Not having to work would be a bonus.
45° adapters are a problem. Trying to make them work caused me to ruin a cable end. The original RD400 cable is closer to fitting through, but the real problem here is the ID of the 45's tube being too small. I don't have a 45° drill bit.
The solution would be to feed the bare cable wire through and then melt on some new ends.
I don't see a solution.
thats tricky for sure.
I used RD 350 angled cable adjusters.
.. were those the ones we cut down?
The straight ones on the RD400 have a much larger ID. They are threaded brass. The Niche Cycle angled ones are a steel tube.
Spent some time destroying one tonight trying to straighten it with heat so I could try to drill it out.
Will have to get a new cable, RD400 one I guess, and find some RD350 angled adjusters that are genuine?
Either that or $700 for the whole kit from Ed Toomey.
I'm still sore about the FedEx bill for almost as much as the split cable that they actually damaged. If they cut an invoice, apparently they have to add $15 to make it worth the cost to invoice.
I'll sleep on it.
On the other hand, if there were such a thing as a "field attachable" cable end, I might be home free.