Hi guys! New member here. I recently shared my RD400F build here.
https://www.2strokeworld.net/forum/index.php?topic=6115.0
I have a few technical questions I hope you all can answer!
-I am on another forum(aircooledRD) and they were quite nasty with me when I told them I am going to run the YPVS/Banshee pistons! I spoke to a rep from Wiseco, and a good buddy that had tens of thousands of miles on a 400 with Prox pistons, and they both said no issue after you trim the center tab off the bottom of the skirt. My machinist is bore matching the pistons at 20 thousands clearance. Is this acceptable?
-I am looking into some exhaust pipes/chambers for the build and it seems there is only one option for the 400F, which is Spec2. Are you aware of any other aftermarket pipes that would fit my bike? I like the spec2 F1 pipe with its stinger type silencer, but $1050 is a bit steep for me.
-I will be premixing with the stock carbs and a y boot/foam uni filter. Exhaust valve removed and oil pump removed(with block offs plate). Stock engine/porting, 1.0mm overbore. What general jetting guidelines can you provide? I am unsure if I will try the stock pipes or shell out a grand for some chambers.
Thanks in advance!
none of that rivet counting here. welcome! as far as exhaust, specII is always an option or JL. (lomas i think sells them for the f)
would recommend better carbs.
Better carbs? Can you please educate me? Are the stock 400F carbs not ideal?
TM32's vm30s, etc. the stock daytona carbs, IMHO, are garbage.
My recommendations:
Since your Daytona looks to be a pretty unmolested bike I would keep the updates simple. And make sure you keep all the stock parts that are removed! The resale value will be impacted by modifications. Stock bikes bring much better money than modded ones.
I agree with Mark, get better carbs. I swapped out the crappy OEM Daytona "2V0" carbs for the superior 76-78 "1A1" Mikuni VM28 carbs. They bolt right in and are easy to tune. I'm running them with a Y-boot and K&N.
I would retain the oil pump. It's a simple task to rebuild the pump.
I agree regarding the carbs. When I had a Daytona with stock carbs, any adjustment to the needles required re-synching them. A set of older RD carbs or aftermarket carbs such as TM's VM30's PWK's etc. will be nicer after you have the jetting figured out.
I concur. Putting TM32s on my RD350B was one of the best mods I ever did.
Gotcha. I am considering other carbs now... Should I stick with the stock earlier vm28's or go up to 30mm? What would you recommend?
Will 32mm carbs affect my low end performance much? I know that with dirt bikes that I tune, the larger the throat size, you give up low end for better top end. Have you notices an effect?
with a stockish motor, not much. i run 32s on mine, but honestly, 30s are fine.
Cool, thank you, i am learning a lot. I would like to use a stock throttle cable, if possible. Will the VM30 and the TM30(flatslides) take the stock cable ok?
Ugh, so I am looking into this and apparently, if I run an aftermarket carb larger than the 28mm, I will need y boot adapters($62!) as the intake bell is larger. Also, the dual throttle cable(no oil injection) is $62! I am thinking stock 400 carbs for best fitment. Is the dual cable necessary or can I use a stock 400 cable and just remove the third oil pump cable?
Adapters
https://www.economycycle.com/shop/yamaha-rz-350/fuel-and-airintake-yamaha-rz-350/air-filters/y-boot-adapters-for-larger-carburetors/
Cable
https://hvccycle.net/yamaha-performance-throttle-cable-for-yamaha-rd-250-350-400-no-oil-pump/
Some advantages of running stock 1A1 carbs:
- One choke lever (Aftermarket carbs have a lever on both carbs)
- Stock RD400 1A1 cables work
- Stock RD400 (2V0 or 1A1) or RZ350 (31K) Intake manifolds work
- Stock RD350 Y-boot can be used to run either a K&N or UNI filter
Okay, great! I am seriously considering some TM28 flat slides. The bells of the carb, both engine and filter side, are the same as VM28's. They are nearly the same price. I assume jetting numbers would be very similar, too.
I do not mind two choke levers.
I am gonna buy the dual throttle cable anyways.
If you can think of a reason for the VM over the TM, please let me know!
none really, tbh. also, you can get cable pull chokes, i have a snowmobile setup on mine with the tm32s
nice flip lever setup but im fussy like that.
Keihin PWK28 are cheaper and better than TM28. They fit the stock airbox boots or y-boot, and are easily modified to work with a standard RD400 cable set (at least they work well with an LC cable, can't imagine the 400 is much different.
Keep the oil pump. It's very reliable, and premixing sucks.
Quote from: SoCal250 on November 29, 2023, 08:27:42 PMSome advantages of running stock 1A1 carbs:
- One choke lever (Aftermarket carbs have a lever on both carbs)
- Stock RD400 1A1 cables work
- Stock RD400 (2V0 or 1A1) or RZ350 (31K) Intake manifolds work
- Stock RD350 Y-boot can be used to run either a K&N or UNI filter
Stock VM28's work great, performance will be fine. If you want to a set of used stockers, I have some.
Do you guys install the engine with cylinders and head on the engine or off? Do both ways work? I removed the cylinders with engine in frame so I was curious to the best method of reassembly.
Also, do you guys prefer the oem black cylinders with polished head? I am liking the blasted look and no paint!!
I have the seat pan all done, had to fiberglass over the rusted out portions.
i mean its all personal preference there.
Screenshot 2023-12-01 at 09-10-56 1975-1978 RD400 CARBON STEEL PIPES AND BILLET SILENCERS (1979 RD400F OPTIONS) Wicked ATV.png
Roger Allen is making pipes for the Daytona if you want something with more modern looking silencers.
https://www.wickedatv.com/product-page/rd400-carbon-steel-pipes-and-billet-silencers (https://www.wickedatv.com/product-page/rd400-carbon-steel-pipes-and-billet-silencers)
Quote from: rodneya on December 01, 2023, 12:15:10 PMScreenshot 2023-12-01 at 09-10-56 1975-1978 RD400 CARBON STEEL PIPES AND BILLET SILENCERS (1979 RD400F OPTIONS) Wicked ATV.png
Roger Allen is making pipes for the Daytona if you want something with more modern looking silencers.
https://www.wickedatv.com/product-page/rd400-carbon-steel-pipes-and-billet-silencers (https://www.wickedatv.com/product-page/rd400-carbon-steel-pipes-and-billet-silencers)
Good to know! I just placed an order with him! Super nice guy who explained everything and sold me on his product. I am sure Spec2 pipes are good pipes, but I really liked Rogers attitude!
Ive got a few Canadian Daytona's. The 2R9 carbs are great.
If you can find any.
No linkage or EPA stuff
The 2R9 VM28 carbs are basically the same as the US 1A1 version, only the jetting is different and if you're doing tuning all that will be swapped out anyway. You'll have a much easier time locating a set of 1A1 carbs.
The 2R9 uses a 169 series primary type needle jet while the 1A1 uses a 175 series bleed type, but interchangeable.
Reference the 20 thousandths clearance, I assume you mean 2 thousandths (0.002"). It will work but don't expect 20'000mi out of them.
My last set of pro x pistons were fitted with 0,0016" clearance (1.6 thousandth), I was very gentle with the break-in process and now have 3500mi on them. While I may not recommend such a tight clearance for others, i would be confortable recommending 1.8 thousandths clearance.
One of my bike has +0.005 clearance of forged pistons and still has good compression and is quiet once I get cruising, the other website doesn't like it!
Quote from: Alain2 on December 03, 2023, 09:09:25 AMReference the 20 thousandths clearance, I assume you mean 2 thousandths (0.002"). It will work but don't expect 20'000mi out of them.
My last set of pro x pistons were fitted with 0,0016" clearance (1.6 thousandth), I was very gentle with the break-in process and now have 3500mi on them. While I may not recommend such a tight clearance for others, i would be confortable recommending 1.8 thousandths clearance.
One of my bike has +0.005 clearance of forged pistons and still has good compression and is quiet once I get cruising, the other website doesn't like it!
Yes, I am sorry. I mis-spoke. I certainly dont expect many miles will be put on the bike. I have other bikes for mile munching and dirt riding. I am still trying to understand why the aircooled forum guys are so against using the prox piston. They were going off! They said the metallurgy was different, expands at different rates, etc..
Quote from: SoCal250 on December 02, 2023, 12:38:00 PMThe 2R9 VM28 carbs are basically the same as the US 1A1 version, only the jetting is different and if you're doing tuning all that will be swapped out anyway. You'll have a much easier time locating a set of 1A1 carbs.
The 2R9 uses a 169 series primary type needle jet while the 1A1 uses a 175 series bleed type, but interchangeable.
I am going to purchase carbs so I am open to ideas! TM, VM, PWK are all options at this point. What would you all recommend for ease of tunability and good performance? It must fit the stock intake manifold and Y-boot!
Let me ask about reed options. Are the stock steel reeds okay for performance and durability? If they come apart, I dont want them grenading my engine.
From my experience, Mikuinis are " ultimately" better carbs w greater adjustment capabilities, But the PWKs are pretty darn easy to set up..I beleive that's why so many people like em. I have a set of 33s on a Banshee .there pretty good w great response.
But in your case I'd recommend 28s! Every RZ I've ever owned..if I went larger than 30 mm was always a few bikes slower accelerating. So your perfect w 28s and pipes...even 26s PWKs. 30+s are good on a modified motor & reed cage.
I'd keep it at 28s and reeds.,👍
I am curious if anyone has a PDF of the 400 F repair manual supplement? I am trying to find head torque and points/timing information. Thanks in advance!
Is this accurate information? Seems a bit light for head torque.
Quote from: SoCal250 on December 27, 2020, 01:52:51 PMCylinder Head Torque Specs
| MODEL | TORQUE SPEC | SOURCE |
| | | |
| RD125 / RD200 | Cylinder head nuts torque: 86.8 ~ 130.2 in-lbs (1.0 ~ 1.5 m-kg) | Yamaha Service Manual: RD125/RD200 1975-76 (LIT-11616-10-12) |
| | | |
| DS7 / R5 / RD250 / RD350 | Cylinder head nuts should be loosened and tightened in a "cross" pattern and in progressive stages with final torque of 180 in-lbs. (2 m-kg). | Yamaha Service Manual: DS7/R5/RD250/RD350 (SVM-360-0800-20) |
| | | |
| RD250 / RD350 | Cylinder head nuts should be loosened and tightened in a "cross" pattern and in progressive stages with final torque of 180 in-lbs. (2 m-kg). | Yamaha Service Manual: RD250/RD350 1972-75 (LIT-11613-61-02) |
| | | |
| RD400 | Cylinder head nut torque: 1.9 ~ 2.1 m-kg (13.7 ~ 15.2 ft-lbs.) | Yamaha Service Manual: RD400 1976-79 (LIT-11616-RD-40) |
| | | |
| RD400F | Cylinder head nut torque:
First: 1.0 m-kg (7.2 ft-lbs.)
Final: 2.0 m-kg (14.5 ft-lbs.) | Yamaha Service Manual: RD400F Supplementary (LIT-11616-01-24) |
Quote from: rearwheelslider on December 11, 2023, 12:24:34 PMIs this accurate information? Seems a bit light for head torque.
Quote from: SoCal250 on December 27, 2020, 01:52:51 PM| RD400F | Cylinder head nut torque:
First: 1.0 m-kg (7.2 ft-lbs.)
Final: 2.0 m-kg (14.5 ft-lbs.) |
Yes, that is correct.
Point gap: 0.30~0.40 mm
Timing should be set to about 2.0 mm BTDC (Stock setting is 2.4 mm BTDC +/-0.15)
Revvy in the house. i need to hear another backfire while cruising the strip in San Jo bro. :)
Victricity! R5 carbs worked on my daytona.
I think i was at a 230 main, 169-p2, 5DP7-5, 30 pilot between 1/2 and 1.0 turns...I don't think it had to be modified for a 2.0 airjet, since it was pre smog, but Mark can confirm. been awhile. Maybe as high as a 35 pilot.
good luck.
Don't remember if i had to change the brass fittings ont he top fo carbs, also bought a premix only cable. 32:1 was what i was running w/ spec II pipes, uni filter banshee crossover and intakes.
I think these new VM carbs have smaller slides...hmm. a little more restrictive?
oh sit. I have RB Design carbs new still in box w/ divider plate, but i need money anyone interested? These are the new VM's modified for an RD, Ron doesn't make them AFAIK anymore...Don't ask me how to jet them...*uck if i know.
Quote from: gardenhosebusabottle on December 11, 2023, 12:44:08 PMRevvy in the house. i need to hear another backfire while cruising the strip in San Jo bro. :)
Victricity! R5 carbs worked on my daytona.
I think i was at a 230 main, 169-p2, 5DP7-5, 30 pilot between 1/2 and 1.0 turns...I don't think it had to be modified for a 2.0 airjet, since it was pre smog, but Mark can confirm. been awhile. Maybe as high as a 35 pilot.
good luck.
Don't remember if i had to change the brass fittings ont he top fo carbs, also bought a premix only cable. 32:1 was what i was running w/ spec II pipes, uni filter banshee crossover and intakes.
I think these new VM carbs have smaller slides...hmm. a little more restrictive?
oh sit. I have RB Design carbs new still in box w/ divider plate, but i need money anyone interested? These are the new VM's modified for an RD, Ron doesn't make them AFAIK anymore...Don't ask me how to jet them...*uck if i know.
Hi uncle reverend kevin! How you be? I just bought some carbs, PWK Keihin 28mm. Hope it doesnt backfire!
Quote from: rearwheelslider on December 11, 2023, 02:16:15 PMHi uncle reverend kevin! How you be? I just bought some carbs, PWK Keihin 28mm. Hope it doesnt backfire!
Good luck w/ those. It looks like you bought PWK30s? is that right?....if so, you probably did good as the larger PWKs also have a larger selection of needles vs. the 28s...that's a GOOD thing. I think when i was tinkering w/ PWK28s i had the timing backwards (my understanding :shocked: at that time), so not much success jetting at that time, obviously.
That B.O.C. concert up at Muckleshoot was cancelled, Buck (guitarist) got sick w/ pneumonia. Will be going back Jan. 27th as it was recscheduled.
I be chillin' 3 day weekends this week and the 2 after that. Had to use my floating holidays up before i LOSE when the New year comes in.
Quote from: gardenhosebusabottle on December 11, 2023, 09:13:37 PMQuote from: rearwheelslider on December 11, 2023, 02:16:15 PMHi uncle reverend kevin! How you be? I just bought some carbs, PWK Keihin 28mm. Hope it doesnt backfire!
Good luck w/ those. It looks like you bought PWK30s? is that right?....if so, you probably did good as the larger PWKs also have a larger selection of needles vs. the 28s...that's a GOOD thing. I think when i was tinkering w/ PWK28s i had the timing backwards (my understanding :shocked: at that time), so not much success jetting at that time, obviously.
That B.O.C. concert up at Muckleshoot was cancelled, Buck (guitarist) got sick w/ pneumonia. Will be going back Jan. 27th as it was recscheduled.
I be chillin' 3 day weekends this week and the 2 after that. Had to use my floating holidays up before i LOSE when the New year comes in.
Guitarists dont need a voice! Weak!