I restored a '76 RD400 (US) back in 2020 and never got around to running it when I was done (I ran into winter and 2021 was a mess).
Some info:
oversized pistons 1 size over
unknown aftermarket exhaust (someone said Coffmans, but I couldn't confirm it)
RD350 y-boot
K&N filter
brass balls removed from carbs
35 pilot jet
310 main
new points
The motor started after the third kick or so. It wouldn't stay idling without keeping on the throttle a little bit. When I put it into gear, I really had to keep on the throttle to keep it running. Away I went. Very little power through full throttle. Into second gear, the engine died. Started again, same thing, very little power throughout the turn of the throttle. I managed to get all of three houses down before riding back with a sad face.
Also, there's oil leaking from the exhaust in cyl 2 (between the pipe and the part that bolts to the engine, connected with springs). I'm really hoping it's just part of the break-in process, but I thought it was important to mention.
Any advice on where to start?
thanks,
Rob
Did you replace the ball with a set screw? Oil from the pipes is kinda common, I think.
I did not. They're left open. I replaced one carb with one from a forum member that had the ball already removed. So I removed the other ball and left it on recommendation from him.
Did you set your timing with a dial gauge?
I would start with double checking it is correct.
I'm still new to mechanical timing. By dial gauge, you mean a micrometer threaded into the spark plug hole, right? I did.
I talked to an old 2 stroker and he immediately said check the timing. Once it cools off a few degrees in the garage, I'll run out to verify.
Is your 310 main really a 210?
310 seems too much.
My good running setup with FPP's, UNI's, boost bottle and update porting:
Quote from: 2steve on June 15, 2022, 08:20:26 PM
Is your 310 main really a 210?
310 seems too much.
My good running setup with FPP's, UNI's, boost bottle and update porting:
Interesting. They're definitely 310. I bought 220, 250, and 310 and the 310 are the ones not accounted for, so they're on the bike.
I can definitely drop down to either of those mains. Based on the setup, Lyn suggested 250-310, so I started at 310. 220 is what was on there when I got it (complete basket case, so no telling if the po ran it with 220s.
Thanks for the advice.
Thanks!
Mine is stock bore and what you could call "below stage 1" porting. So, do be careful.
dumb question. did you make sure the slides are in the carbs the right way. easy to mix up, the cutout needs to face the air filter. IF they dont, swap the left and right slides.
310 seems really steep on the main but verify the slides, then timing then test ride.
reason i say slides is the idling bit. .02
Whoa whoa whoa. The cutout on the slides? Are you saying the groove alone the side of the slide faces the right (brake) side of the bike?
There's a tiny nub in the carb body that I figured (apparently incorrectly) corresponded to the groove along the side of the slide.
If the cutout means the sloped part of the bottom of the carb, they are indeed in backward.
Edit: or the slides are swapped between carbs :bang:
I believe that 99% of 'us' have done that at one time or another...
swapped between carbs. like said, it happens.
in this pic of the carb cutaway, the air filter would be towards the right. :cheers:
(https://www.2strokeworld.net/wp-content/uploads/general-tech/carb-cutaway-vm28.jpg)
Quote from: m in sc on June 16, 2022, 01:06:00 PM
swapped between carbs. like said, it happens.
in this pic of the carb cutaway, the air filter would be towards the right. :cheers:
(https://www.2strokeworld.net/wp-content/uploads/general-tech/carb-cutaway-vm28.jpg)
That's exactly what happened. Thank you so much for that.
Now I'm getting a flat spot around 1/4 throttle, so I'm looking at the needle position.
Right now it's the second slot from the top.
good, glad it was simple.
run it to the second from the bottom. (4th position). always better to err rich when testing. if its blubbery, then it has to be the middle :cheers:.
Quote from: m in sc on June 16, 2022, 01:23:38 PM
good, glad it was simple.
run it to the second from the bottom. (4th position). always better to err rich when testing. if its blubbery, then it has to be the middle :cheers:.
2nd from the bottom was too rich. Moved to the middle and swapped the 310 mains for 250 while I was in the garage.
It pulled much, much better... Until I ran out of gas as soon as I left my neighborhood. I fueled it up a bit and had a somewhat difficult time starting it. When it started, it was even more sluggish than before. Came home and found the plugs are oily. So I swapped them out for fresh ones to be sure they're not the problem.
It's still over 100 here on the wet bulb, so I think I'm done for the day
gotcha. you're getting it!. HVAC guy by chance? ('wet bulb' comment).
Quote from: m in sc on June 16, 2022, 04:58:40 PM
gotcha. you're getting it!. HVAC guy by chance? ('wet bulb' comment).
Not by a longshot. Just really in tune to the weather saying it's 93 and walking outside and saying "well, that's bullshit"
*Oops, I realize I said wet bulb when I meant heat index. The damn heat is getting to my brain.
I still can't get this bike moving.
After reversing the slides to the correct orientation and side, moving the needle to the middle notch, and swapping the 310 mains to 250, it still just won't move. It seems to run just fine when it first starts, but after a few feet, it won't go above ~3200rpm.
Fuel is flowing, oil is flowing. After a few minutes, it won't even idle.
If I let it rest, it starts and will go above 3200rpm in neutral, but bogs down as soon as I'm on the road.
It may seem like a simplistic question, but are you certain both cylinders are firing all the time?
Going by the exhaust, yes. And I can pull up where the throttle cable attaches to the carbs and each causes the rpm to increase. But even then only to around 3200rpm
Possibly fuel starvation caused by fuel tank vent hole being blocked? Try taking fuel cap off and see if it makes any difference.
id take carbs apart and verify the airjet in each carb is cleaned and the jet tube is clean (still).
just to eliminate it.
Quote from: m in sc on June 17, 2022, 03:45:10 PM
id take carbs apart and verify the airjet in each carb is cleaned and the jet tube is clean (still).
just to eliminate it.
Yessir, that needs to be done on a 400, regardless.
well the brass balls were taken out prior, but since it sat a bit worth another look. :twocents:
Quote from: BlueR32 on June 17, 2022, 03:43:21 PM
Possibly fuel starvation caused by fuel tank vent hole being blocked? Try taking fuel cap off and see if it makes any difference.
I replaced the fuel cap with a (new) spare I had from my xs750 thinking the same thing
Quote from: m in sc on June 17, 2022, 03:53:39 PM
well the brass balls were taken out prior, but since it sat a bit worth another look. :twocents:
Can't hurt, I suppose. But if the RS carb is blocked, I'm blaming you haha
I'll also take a closer look at the timing, since I've gone down the fuel path so far.
Thanks everyone for the help. I'm determined to get this thing over 30mph.
Also going to check the floats while I've got the carbs off. You never know.
Unfortunately a more pressing issue has come up on this journey. I have no rear brake pressure. I rebuild the better of the two master cylinders that came with the bike (in a box like many things), and I should have known better.
Now I have to decide on custom fitting a cheap ebay special, getting one of these sleeves, or forking over the $$$ for the HVC Cycle replacement.
Quote from: ElFuegoBlanco on June 17, 2022, 03:22:09 PM
Going by the exhaust, yes. And I can pull up where the throttle cable attaches to the carbs and each causes the rpm to increase. But even then only to around 3200rpm
Feel the exhaust pipes or heads to make sure both sides are firing. Don't burn your hand while testing.
BTW I just got an RD400 running. It was only running on one cylinder. I kept thinking, air, spark, gas. Cleaned the carb, still not running. Then I realized I had not torqued one intake sufficiently and the air was bypassing the carb, going around the reed gasket. Torqued up the four bolts and now the bike runs great.
Now that is interesting. I'm 95% sure they're both firing, but I'm definitely going to keep this in mind.
I would have to go back and re-read the various write-ups on the "balls out" procedure, but remember that the balls got replaced with set screws on mine. Removal of the balls not being the object of this procedure but rather access to the orifice behind them. The only other thought would be to check that the exhaust is not obstructed. Was lucky with my '76 in that the basket case came together and runs beautifully. It has stock exhaust, though.
heres the thing.. w out the stock airbox & the lines run back to it in theres no reason to close the holes back up. :twocents:
250 main jet is still a huge jet. Not revving out under load is a typical sign of being rich. I just went through the same thing on my bike. Dave F modded 350. I'm headed back down to around a 190 or 200 main.
Quote from: Striker1423 on June 18, 2022, 10:52:15 AM
250 main jet is still a huge jet. Not revving out under load is a typical sign of being rich. I just went through the same thing on my bike. Dave F modded 350. I'm headed back down to around a 190 or 200 main.
I might just do that. At least down to 220. I definitely have a stuck float though. I managed to leave the petcock open and woke to a pool of fuel on the ground.
Once I get the brake situation sorted, I'll fit a new float and see where I stand. If it's still rich, I'll go down to 220. Thing is, I'm not even sure if it's getting to the mains. After the first few minutes of running, it won't even rev in neutral
Rob
thats probably the float creeping fuel in. def get that sorted 1st.
Rear brake is back in action. I managed to fit an ebay MC with only a little bit of frustration.
Waiting for float needles and a replacement throttle cable from economy (the carb end of my cable are kinked a little and the price of the cable dropped). Once they're in, I'll be back at it.
Some down time to work on the xs750
did you buy that XS750 that was wrecked at the gap recently? just curious.
Nah, I've had this one since 2008 or so. It somehow keeps running so I keep riding it.
Unfortunately the Yamaha Triples forum that had a huge amount of knowledge went away unexpectedly and a lot of information on these old bikes was lost. It makes me happy this forum and the UK forum are still active.
While I'm waiting for a new throttle cable and float valves to ship from Economy, I'm verifying the timing.
What does everyone recommend for the timing on this bike?
It's a 76 rd400 with aftermarket exhaust, rd350 y boot k&n filter, one size up pistons. I'm not sure what other info would be relevant.
Thanks! Rob
2-2.1mm btdc.
Awesome, thanks. I'll go ahead and set it today. Hoping the parts ship soon so I can get back to it.
Back to the reversed slides experience, I like to forget to hook up the choke crossover:)
Maybe make sure your floats are actually floating while you are in there as well. The float shutoff valves that are all metal never seem to cause issues for me but maybe I'm just lucky.
If your floats arent floating, the local small engine sling blade swears by SealAll. I've used it a few times and dont remember having to go back and fix anything. Its like a thick, old school model glue with a good bit of solvents in it, I keep it in a jar after the tube is opened. Make sure the floats are dry inside first.
I've had the float needles fail on my xs before. It explains why I have a bag full of 5 or 6 float needles that don't fit the rd, unfortunately.
Both floats do float. They both look to be in good shape, too.
As for the crossover, I'm sure it was connected, but I have been having choke issues. The choke won't stay actuated. When I release the lever, the choke disengages. I don't think it's related, just an observation.
The new float needles/seats and throttle cable should be in on Friday. Unfortunately, with the throttle cable price dropping by $100, it pretty much immediately went on back order. So I switched the Economy order to an aftermarket cable.
Well since mine is on the floor in pieces, this is mine open and closed, 77 400, pretty sure stock. It will definately stay on riding it slowly, warming it up, I dont remember if it vibrates closed if you forget to close it, feels like it might but I think I can ride it with it on. The little cam like arm is pretty stiff and, without looking it up, I'd guess is what makes it "spring" closed or open.
(https://i.postimg.cc/KjP0pTZb/20220629-212852.jpg) (https://postimages.org/)
(https://i.postimg.cc/4xsx0R1R/20220629-212841.jpg) (https://postimages.org/)
yes thats stock. make sure OP that the spring is above the lever perch like in pic, not below it, ive seen that mistake a lot.
Quote from: Clem710 on June 29, 2022, 09:46:53 PM
Well since mine is on the floor in pieces, this is mine open and closed, 77 400, pretty sure stock. It will definately stay on riding it slowly, warming it up, I dont remember if it vibrates closed if you forget to close it, feels like it might but I think I can ride it with it on. The little cam like arm is pretty stiff and, without looking it up, I'd guess is what makes it "spring" closed or open.
(https://i.postimg.cc/KjP0pTZb/20220629-212852.jpg) (https://postimages.org/)
(https://i.postimg.cc/4xsx0R1R/20220629-212841.jpg) (https://postimages.org/)
Thank you! The pictures were exactly what I needed to figure out what was going on with the choke lever. The spring arm was in the right place (thanks M) but had nowhere near the same angle as yours relative to the lever. the lever would almost get caught by the cam, but failed to catch more than half the time You're right, it's quite stiff, so I don't know what happened to it. Maybe left in the actuated position for 35 years? I removed it and bent it just slightly upward to match the angle in your pictures and it seems to be much more functional now.
Parts are scheduled for early delivery today, so I should be back to turning wrenches very soon.
Rob
Looks like I'm back to square 0 or -1.
Fitted the new throttle cable, calibrated the oil pump gap, set timing to 2mm btdc.
It started on the second kick but I'm sure I blew a head gasket on the rh cylinder. Smoke is coming out between the head and cylinder. Oil is dripping down both exhaust headers
:bang: :help:
Edited to add: I still have compression on both cylinders. They're identical at 110psi
Edit 2: whoops, that was at closed throttle. At WOT, they're 120psi.
retorque the heads. 18-20ft-lbs, you can also spray some permatex copper gasket sealer on them.
Quote from: Striker1423 on July 01, 2022, 11:50:44 AM
retorque the heads. 18-20ft-lbs, you can also spray some permatex copper gasket sealer on them.
Are you saying to remove them, spray permatex on the gaskets, then reinstall and retorque?
I would remove them, clean them, spray with permatex copper (2-3 coats each side), reinstall and torque to 18-20ft-lbs.
Quote from: Striker1423 on July 01, 2022, 12:15:20 PM
I would remove them, clean them, spray with permatex copper (2-3 coats each side), reinstall and torque to 18-20ft-lbs.
Thanks for the advice. Not how I was hoping to spend the weekend, but that's life.
Any idea what could have cause it?
Pulling the heads to look is easy. Are you positive the head gasket is leaking? The thing is, if you had that big of a leak, the head was either loose, or it's warped. Cause 120psi is good compression. If the head was leaking enough, you'd be seriously low on compression.
Before going too far, I'd check to make sure your exhaust gaskets are good, and also check to make sure the exhaust headers aren't leaking at the flange first. Those leaks will sometimes waft upwards and make it look like your heads to blame. Also, oil pouring down the cylinder from the exhaust flows all over when you ride. Could explain that too.
+1 Agree with what Striker said
Also make sure that after the engine has been run (heat cycled) that you re-torque the head bolts. :twocents:
I'd say I'm sure. It's blap blap blapping out the side of the motor between the cylinder and head.
I wish my camera wasn't busted (and that my new phone arrived on time this morning instead of being shipped to Indianapolis (I'm in WV lol)) or I'd take a video of it. I'll go ahead and pull the heads to take a look. I know it's not hard, more like an inconvenience. It wasn't leaking before this last bit of work. All I did was change the throttle cable, change the timing from 2.2 to 2.0mm, and chang the float valves.
Quote from: SoCal250 on July 01, 2022, 01:28:32 PM
+1 Agree with what Striker said
Also make sure that after the engine has been run (heat cycled) that you re-torque the head bolts. :twocents:
I haven't retorqued the heads since installing them. I'll try that first just to be sure.
You can retorque the heads sure, but I would recommend you check and clean the gaskets before just applying torque. The leak will build up crap on the gasket surface.
Quote from: Striker1423 on July 01, 2022, 01:49:43 PM
You can retorque the heads sure, but I would recommend you check and clean the gaskets before just applying torque. The leak will build up crap on the gasket surface.
Will do. Thanks for the advice. Tank is off, I'm off to get some permatex copper.
You can also anneal the copper head gaskets if they're being reused.
Anneal and clean gaskets, make sure heads are flat, check to see if cylinder is flat, be sure head studs are clean and that the bolts thread easy, make sure you use the washers. Reinstall and tighten slowly and evenly in an alternating crisscross manner, use a torque wrench and just keep going back and forth. Theres probably a pic in a manual for which order to do them in but I doubt most people follow it.
Assuming its sealed, heat cycle, then check em all again. I try em at the low end of the spec kinda thinkin that its less likely to warp the head and I can always go up but thats probably all meaningless if you do it evenly.
Sometimes I'll use a very thin film of goop on ones that dont like to stay in place. Permatex copper certainly doesnt hurt anything. In theory, neither should be necessary.
Doing them slowly and evenly is the trick imho.
Done probably less than a 50 so not a pro, there are certainly plenty of them here though, you can always check the manual, it should be in there:)
If you are up in the panhandle or at least above Wheeling, I'm not far at all and could help, but again, not a pro, just patient and persistent. Been done quickly in the pits by racers 1000s of times so you should get it.
Lol, I type too slow but here it is in one place:)
Annealed and sprayed with permatex copper spray. I wasn't fast enough to read the reply saying to just anneal.
So, now that permatex has been sprayed, how long should I wait before installing? The can just says to let the solvent to evaporate before installing.
Quote from: Clem710 on July 01, 2022, 02:17:17 PM
If you are up in the panhandle or at least above Wheeling, I'm not far at all and could help, but again, not a pro, just patient and persistent. Been done quickly in the pits by racers 1000s of times so you should get it.
Thanks for the offer. I'm farther down, south of Morgantown.
retorque and check again
Quote from: m in sc on July 01, 2022, 03:14:37 PM
retorque and check again
Okay, so I'm back to where I was at the very beginning of this thread. Heads are torqued down and the leak is fixed. But it just won't rev under load. In fact, my driveway is sloped and I can't even get it up to the road. It bogs down to the point where it dies (this is new, it didn't die before, but I wasn't trying to get it up the driveway).
I can't think of what I'm missing here. Here's where I am:
Moved from 310 mains to 250
Moved needle clip from second notch from the top to second to the bottom, then the middle, then back to second from the top.
Cleaned the carbs again
Swapped the throttle cable (the carb ends where pretty bent up)
Swapped the float valves
Moved from 2.2mm btdc to 2mm
Checked and rechecked the oil pump gap
I haven't changed the reeds. They looked to be in good shape when I got the bike,though they are probably original.
Correction:
In neutral, it won't rev over about 5k rpm. If I hold the throttle open for a second, it drops to about 4300 rpm and won't go any higher.
When I first started it and revved it in neutral, I didn't rev it too much and the throttle response gave me the impression it was going much higher. I don't think that's changed, I think I just wasn't paying close attention to the tach. It's also loud as hell, even at 5k rpm.
Speaking of loud, there is no baffle material in the exhaust. It all burned away years ago.
The tach also bounces about 500 rpm at idle. It mellows once I open the throttle a little.
i think your timing is way off or something.
Quote from: m in sc on July 01, 2022, 06:52:43 PM
i think your timing is way off or something.
I certainly can't rule it out, because something is still wrong. I'm using a buzzetti micrometer to set it. I'll ask around town to see if anyone has a dial gauge or I'll go ahead and buy/modify one.
can you get a timing light? to me, easiest and most repeatable way.
After you get the timing confirmed, below for your reference is my current RD400 configuration, which aside being a Daytona is very similar to your setup. My Daytona has the standard 76-78 carbs on it. We may even have the same pipes. I'm a little on the rich side but I prefer safe tuning.
Elevation: Sea level
RD400F
0.25 over pistons
Autolube pump operational
New OEM points, Timing at 2.0mm
Aftermarket vintage chambers (unknown brand, Coffmans?)
1A1 carbs
Y-boot with K&N
And if I remember correctly, here's what I'm running after swapping out the stock Daytona carbs for the standard 1A1 RD400 Mikunis:
250 main jet
30 pilot jet (thought I was running 32.5 but the last tuning notes I have says 30)
stock NJ & JN (175 P-2 & 5L1) - clip #4
Air screws: 1 turn out
Floats set at 23.5mm
Quote from: SoCal250 on July 01, 2022, 07:26:55 PM
After you get the timing confirmed, below for your reference is my current RD400 configuration, which aside being a Daytona is very similar to your setup. My Daytona has the standard 76-78 carbs on it. We may even have the same pipes. I'm a little on the rich side but I prefer safe tuning.
Elevation: Sea level
RD400F
0.25 over pistons
Autolube pump operational
New OEM points, Timing at 2.0mm
Aftermarket vintage chambers (unknown brand, Coffmans?)
1A1 carbs
Y-boot with K&N
And if I remember correctly, here's what I'm running after swapping out the stock Daytona carbs for the standard 1A1 RD400 Mikunis:
250 main jet
30 pilot jet (thought I was running 32.5 but the last tuning notes I have says 30)
stock NJ & JN (175 P-2 & 5L1) - clip #4
Air screws: 1 turn out
Floats set at 23.5mm
I gotta say, that does sound just like my setup. I think my air screws are 1 1/2 out, though. I don't know the needle jet or jet needle, but I have to assume they're either stock or they were replaced at some point while the bike ran.
Quote from: m in sc on July 01, 2022, 07:08:31 PM
can you get a timing light? to me, easiest and most repeatable way.
Working on that now. I picked one up from hf, but I've never needed to use a timing light, so I'm off to YouTube haha
Thanks everyone for your help. Hopefully I'll get it sorted soon.
Rob
Have you done a leak down test? I am reading through the thread and I am not seeing where you have. I would start there and work up. You'll be chasing your tail if you're sucking air somewhere.
Quote from: irk_miller on July 02, 2022, 08:09:36 AM
Have you done a leak down test? I am reading through the thread and I am not seeing where you have. I would start there and work up. You'll be chasing your tail if you're sucking air somewhere.
I haven't. I don't have a leakdown test setup for a 2 stroke. I've seen some homemade stuff out there, though.
Possible but unless the air leak is massive, you won't be limiting revs. You'd be idling at 4-5k rpm consistently though lol. Saw a buddy's old Yamaha Phazer snowmobile motor running at like 4k at idle and when we finally convinced him to look, the right cylinder base gasket was hanging out
Quote from: ElFuegoBlanco on July 02, 2022, 08:51:44 AM
Quote from: irk_miller on July 02, 2022, 08:09:36 AM
Have you done a leak down test? I am reading through the thread and I am not seeing where you have. I would start there and work up. You'll be chasing your tail if you're sucking air somewhere.
I haven't. I don't have a leakdown test setup for a 2 stroke. I've seen some homemade stuff out there, though.
I am a novice at 2 strokes, so I can only speak from the issues I have been having, which have been similar. Two major culprits were timing and an air leak under the left reed cage. The bike idled extremely well. The plugs were even a nice toasted color as though the mix were pretty damn near perfect. I chased my tail for a solid week trying to figure it all out. Did a leakdown and the air went straight through. It seems crazy bad to leak like that but idle normally or even well. However, it was a combination of retarded timing and the air leak. Once you got on throttle, there was no power. It would eventually take off once you hit 5k, but not half the power it should've had. Just food for thought. Air leaks are often the culprit for inconstent issues, as variables tend to be wild. My kit is made from pvc parts, two 1 1/4" freeze plugs and a low psi gauge from Home depot with a schrader valve in one of the carb plugs.
Okay, I've thoroughly confused myself. Can anyone refer me to a good writeup on how to check the timing with a timing light?
I guess my confusion is this-
I set the timing 2.0mm btdc.
1. Should the timing mark on the stator(?) match the mark on the plate at TDC? Or 2mm BTDC?
2. When I aim the timing light, should the marks line up?
I think I'm overthinking this whole thing.
Quote from: irk_miller on July 02, 2022, 11:29:59 AM
I am a novice at 2 strokes, so I can only speak from the issues I have been having, which have been similar. Two major culprits were timing and an air leak under the left reed cage. The bike idled extremely well. The plugs were even a nice toasted color as though the mix were pretty damn near perfect. I chased my tail for a solid week trying to figure it all out. Did a leakdown and the air went straight through. It seems crazy bad to leak like that but idle normally or even well. However, it was a combination of retarded timing and the air leak. Once you got on throttle, there was no power. It would eventually take off once you hit 5k, but not half the power it should've had. Just food for thought. Air leaks are often the culprit for inconstent issues, as variables tend to be wild. My kit is made from pvc parts, two 1 1/4" freeze plugs and a low psi gauge from Home depot with a schrader valve in one of the carb plugs.
This definitely matches what I'm seeing. I posted on the local vintage mc fb group asking for help troubleshooting. Hopefully someone nearby has a 2 stroke leakdown tester so I can go down that route.
Quote from: ElFuegoBlanco on July 02, 2022, 03:34:46 PM
Okay, I've thoroughly confused myself. Can anyone refer me to a good writeup on how to check the timing with a timing light?
I guess my confusion is this-
I set the timing 2.0mm btdc.
1. Should the timing mark on the stator(?) match the mark on the plate at TDC? Or 2mm BTDC?
2. When I aim the timing light, should the marks line up?
I think I'm overthinking this whole thing.
"Timing Light" can have two meanings. It depends on how you're setting/checking timing -- static (engine off) or dynamic (engine running)
--- With a dial gauge you are doing static, and the timing light used is a simple test light that shows when the points open (the light turns on). You can also use a digital mutli-meter or a buzzer.
--- With an automotive timing light (inductive timing gun) you are verifying that timing is set at the spec you wanted while the engine is running.
When you set the timing with a dial gauge and test light (or DMM), first you find TDC and then you want to adjust your points so they just open at 2.0mm BTDC (or whatever the desired timing setting is that you want to meet). So in the case of an RD400 on today's fuel this would be something like 2.0mm or 2.1mm BTDC.
When you have located TDC and then rotated the engine back to 2.0mm BTDC you will want to adjust the little timing pointer so the lines match up at your desired timing setting. If the adjustable timing pointer on the ignition is still in it's stock position then it would be aligned at 2.3mm BTDC (since the factory spec was 2.3mm for the RD400C/D/E)
If you're looking for a cheap and easy test light setup for static timing, here's what I've been using for 15 years or so:
Gardner Bender GET-202A low-volt tester & a pair of test leads with alligator clips to use as extensions.
With this I can just lay it on top of the engine case or wedge the test light housing between the cooling fins for easy viewing while I'm turning the crank.
And I use a Central Tools #6491 dial gauge kit. It's made specifically for two-strokes and the gauge face is small enough that I can do most bikes without removing the tank.
And then, afterwards I double-check with a Craftsman inductive timing light while it's running to verify that the marks line up.
Don't confuse 2mm of rotation (not what is set) with 2mm BTDC piston movement (what we set timing to). Mine was set while building the engine, still on the bench, and haven't touched it since.
Thanks for the great writeup. This is exactly what I was looking for.
I went through all of it again just now:
On the left cylinder, set the gauge at zero at tdc
Back off the motor moving the crank clockwise
Set the gauge at 2.0mm deeper
Move the crank counterclockwise until it stops (using a buzzetti micrometer, my attempts at making a dial gauge fit have failed, badly. maybe time to break down and buy one)
Set the point (orange wire) so that a test light illuminates just at this position
Set the marker on the rotor
Repeat the process for the rh cylinder
I did find that somehow the lh cylinder was a bit out. I've set it three times in the last week. I don't know.
Fire it up.
Connect an inductive timing light to the left plug wire.
The timing mark on the rotor is way off to the right and bounces quite a bit. I let it warm up a bit. Move the point plate until the marker lines up.
Repeat for the right cylinder. This one is more stable, but still to the right of the plate marker. Adjust until it lines up.
Similar result. It runs smoother, but still won't rev over 5k. It's also idling at 3k now. If I press the choke lever down, it calms down to about 1800 rpm. Lift the choke lever, and it stays there until I rev the motor, then idles at 3k again. All of this is new today. It was idling much lower yesterday.
If you are usng the correct procedure with the dial gauge you shouldn't need to move anything when you check it with the engine running. The timiing marks should line up when checked with the inductive timing light.
Not sure what you mean about "Set the gauge at 2.00 mm deeper" but maybe this will help. I hope my explanation below makes sense
When looking at the ignition points plate, the contact point on the left is for the left cylinder and the one on the right of the plate is for the right cylinder.
The engine normal rotation is anti-clockwise when viewing the points plate. So to turn the engine forwards, turn the crankshaft bolt anti-clockwise or to turn the engine backwards go clockwise.
Here's the quick rundown on using the dial gauge to set timing events:
1) Insert the dial gauge into the plug hole (make sure it can't move or shift)
2) Rotate the crank around until you find TDC. (You will see the sweep of the needle change directions, where it stops between changing direction is TDC)
3) Set the gauge to 0.00 at TDC
4) Rotate the engine backwards, watching the dial gauge until you are passed 2.00. I usually go back to about 3mm and then approach the 2.00mm mark as this will eliminate any potential error from crank slop. When the gauge is exactly on 2.00mm away from 0.00 the points should open for that cylinder (the test light will turn on). You will want to loosen the points screws and adjust so the light comes on exactly at that position.
I usually repeat this several times until the light turns on exactly where I want it. It will take several tries because very slight movements of the plate will move the timing event.
5) I also make sure that my timing point marks line up when I'm at 2.00mm BTDC
6) Repeat the process using the light for the other side. No need to adjust the timing pointer on the other side because it should already line up since you're crank is 180 degrees.
NOTE: Since we went BEFORE TDC, after you have zeroed out the gauge at TDC you will be subtracting 2.00mm On my gauge that is two full sweeps of the large needle beckwards.
Quote from: SoCal250 on July 02, 2022, 06:34:41 PM
If you are usng the correct procedure with the dial gauge you shouldn't need to move anything when you check it with the engine running. The timiing marks should line up when checked with the inductive timing light.
This is the point of my confusion in the process, since I am getting such a different reading with the light.
I've gone over the buzetti gauge steps over and over. They're really not hard.
Insert the gauge
Set it at zero
Rotate the crank counter clockwise until the post reaches its highest point.
Tighten the set screw
Back off the crank
Rotate the gauge dial two full rotations for 2mm (1/10 rotation=.1mm)
Rotate the crank counterclockwise until it hits the gauge
It really is that simple, as I understand it.
So why the timing would be so far off when running, I don't know. Bad plug wires or caps? They're undoubtedly original. Bad coils? I ohmed them out and they're within spec, but again, likely original. I don't even know if coils or plug wires would cause the timing to be off when running vs not. I do know I've had bad performance problems with bad plug wires, but I don't know enough about it to say if it would cause what I'm seeing.
So maybe a bad gauge? That's possible. They have a great reputation, but who's to say?
when the marsk line up riunnign the timing is good enough to diagnose the rest.
its on the carbs i think since that is sorted. what is the exact carb setup? jet tubes, needles (stock? rebuild kit ones?) etc.
Quote from: m in sc on July 02, 2022, 07:57:01 PM
when the marsk line up riunnign the timing is good enough to diagnose the rest.
its on the carbs i think since that is sorted. what is the exact carb setup? jet tubes, needles (stock? rebuild kit ones?) etc.
As far as I know, everything is stock with these exceptions:
Main jet: 250
Pilot jet: 35 (I completely forgot I changed the pilots to 35)
I haven't replaced any other jets or the needles.
I'm read up on building a diy leak down tester, so I'm off to the hardware store in the morning.
did you pull the jet tubes completely out and clean them and the air jet?
Quote from: m in sc on July 02, 2022, 10:40:13 PM
did you pull the jet tubes completely out and clean them and the air jet?
That's an excellent question. Honestly, I don't remember if I did that when i did the carb work in 2020. I'll give it a go in the morning.
Thanks!
Unfortunately, no progress today.
I gathered the materials for a leak down test, so hopefully I'll run it in the morning.
One thing I found funny is I put a plug cap in my pocket so I'd remember to pick some up from the auto parts store while I was out. I reached into my pocket and found insert had worked itself out of the cap. I'll be pretty disappointed in myself if a shoddy cap is the root of my problems.
Once I get the leak down tester together, I'll post some pictures for anyone who needs them
the cap is likely. i had one take a shit on me one time, temporarily fixed it with a part of a cigarette wrapper, the tinfoil (years ago).
Quote from: m in sc on July 03, 2022, 06:05:53 PM
the cap is likely. i had one take a shit on me one time, temporarily fixed it with a part of a cigarette wrapper, the tinfoil (years ago).
That's awesome.
I was in the parking lot of the hardware store and reached into my pocket and pulled out the threaded insert of the plug cap. I stood there for a solid minute before I realized what it was. It's like I've definitely seen this before but what is it, where did it come from, and how did it end up in my pocket.
Hopefully new plug wires and caps will do the trick.
Leak down test has finally been performed.
There was a leak in the left side reed cage. Cleaned up the surfaces with fine san paper and it's good to go.
What's not good to go is the left side crank seal. There's a small amount of air leaking out.
Where do I need to go from here? The seal was replaced when the engine was rebuilt. I don't suppose there's some weird trick that doesn't require removing the motor and splitting the case? Right?
Over fifteen minutes or so, the pressure dropped from 5psi to 2. Still very slowly bubbling out of the seal.
Leaky fork seals can sometimes be sealed by sliding a piece of 35mm film GENTLY under it and cleaning out bug guts. I doubt you have debris fowling the crank seal. More likely a bur on the shaft or carelessly installed.
Quote from: pidjones on July 04, 2022, 02:58:29 PM
Leaky fork seals can sometimes be sealed by sliding a piece of 35mm film GENTLY under it and cleaning out bug guts. I doubt you have debris fowling the crank seal. More likely a bur on the shaft or carelessly installed.
Careless installation is the story of my life. I'm wondering now if the seal was installed backward, but I've seen a lot of conflicting information out there on it. Either way, it's looking like I'm splitting the cases. But for what it's worth, the spring on the seal is on the outside of the case. Along with the printing. I'm 99% sure I verified it was correct when I installed it. It was from the "Sudco/ARS Engine Oil Seal Kit for Yamaha RD400/350/250 R5/DS7" from Economy.
glad you caught the leaks but i seriously doubt that the cause of the running issues you are describing.
Quote from: m in sc on July 04, 2022, 03:47:00 PM
glad you caught the leaks but i seriously doubt that the cause of the running issues you are describing.
I'm in inclined to agree, but I'll add that the leak at the intake was pretty bad. So at the very least, that was a problem I'm sure.
So what now, then? Put it all back together, hope for the best on that seal, and continue looking for the root of the performance problem? Yank the motor and replace the seal, focusing on the performance problem along the way?
Thanks for your help everyone. I'll be owing some homebrew beer or home roasted coffee to people here by the time this is done.
Quote from: m in sc on July 02, 2022, 10:40:13 PM
did you pull the jet tubes completely out and clean them and the air jet?
I think m in SC is the winner here. I did pull the tube from one carb when I rebuilt it. But obviously not the other. It was the grossest carb part I think I've ever seen. I really don't know how in the 25 times I've disassembled it I never removed the tube to clean it.
I'm still going to replace the plug wires and caps tomorrow. And I'm inevitably going to have to split the case to replace the oil seal. The parts are on order, but until then, let's see what happens.
I pulled the motor to replace the leaking seal. Unfortunately, I forgot to order wrist pin clips. I realized today I have OEM clips, not Wiseco clips, and only 2 of them. So they'll be here next week. I wish I would have realized it last week.
It probably would be fine since there's only a total of about 5 miles on the motor since I installed the pistons, but why risk it.
I've been reading up on the correct way to tune the carbs, so hopefully I'll have better luck this time.