Hi. I'm new here, joined in the hope to get some help and hopefully learn a lot about 2 strokes. I inherited a 88FZ600 with a 76 RD400 newly rebuilt, never started motor. I believe this will turn out to be a fun build and a very nice, different bike to ride around in. I was hoping for your expertise in getting me a list of the electrical parts I'm going to need. Don't have much experience in 2 strokes except riding dirt bikes. Have 2 street bikes, 4 strokes which I have been doing all the mechanical work for. The bike has the wiring harness, which I know will have to be adapted.
So battery, coils, fuse box, points, condenser, reg/rectifier (?), 2 stroke oil tank.
I'm sure there's something else I need. Thank you for your time.
When I figure out how to post pictures I will.
As I mentioned in prior post. I am putting a fresh rebuilt 1976 RD 400 in 88 FZ600U frame. Motor mounts are all done. One problem is I have a box of electricals from both bikes and don't know which is for what or where they go. If anyone can help me sending a picture of these items on a RD400 frame it would definitely help figuring which ones belong to the RD. Thanks.
there's a wiring diagram on the tech library for sure. for 400s.
I've done an rd motor in a ninja frame a long time ago, wiring was pretty easy.
usually the forum isn't this glitch just fyi
If you have complete wiring harnesses for both FZ and RD, I would think the FZ harness would have mostly multi-pin connectors vs the RD which would be mostly bullet connectors. Hope this helps!
Thank you all for the great ideas. Maybe I'm making it worse, but my concern is where the original electrics were mounted on the FZ and in the RD and what do they look like, as I have a box full of mixed items, so I can sort the pieces that I have.
Any ideas will help as I am new at this. Thanks again.
I would think you'd want to use the RD harness for your build as that will match up with the charging system of the motor. If you go on the Partzilla website and search for the correct year Yamaha RD400 and the Electrical page you'll get a detailed parts fiche with pics of the various components.
https://www.partzilla.com/catalog/yamaha/motorcycle/1976/rd400c/electrical
Hope this is helpful. Another option would be for you to post pics of the parts you can't identify and the forum will chime in. Good luck with build!
Thanks Blue for pointing out that parts fiche. The picture is pretty explanatory of the parts I need.
When I figure out how to post pictures I will.
you cna use all the stock rd charging ignition stuff. its gets different if you have an aftermarket cdi ont he 400 motor in some ways, a lot easier. i assume the ignition/charging on the 400 motor is stock?
The wiring for these 70s style bikes are pretty basic. Definitely need a battery for these things unless you get a vape or hpi system, but a small alarm battery will work well.
Yes m, the motor is a completely stock rebuild.
I'll definitely get it started with a premix just to be sure. Then i'll make sure pump is working correctly. Maybe further down the line I'll get information on either a hpi or vape system.
Thanks again for the insight.
yeah as long as you use an rd400 regulator/rectifier, all the motor needs is 12v to the coils to run. the fz uses a cdi and a different reg/rectifier (obviously). thats important because I think the fz system key and kill work by grounding the ign circuit to kill the motor. imho, the easiest way around that is use a relay to power the coils using a a switched ground wire to control it. beyond that, you just need a switched 12v source and a direct lead from the regulator to the battery. the rest, you can use the stock fz harness. the tach on that is.. electronic? if so, prob wont work. however, if its cable,, the ratios will be the same. good luck w it. these are the fun ones for sure.
Thanks for all the advice. Found the original RD 400 wire harness and most of all the needed electrical parts. I do have a problem selecting the correct carburators from a box of about 8 of them.
Can someone post a picture of the correct carb so I can choose ? Do both have a choke lever or just the left hand side one with some type of connecting bar to the right one??
VM28s, one choke lever on left carb, there a tube that joins them. carbs should be stamped 1a1 if i am correct, back side of the choke tower on the flat spot of the casting
RD400 carbs:
Thank you guys. That helps me a lot in choosing the correct carbs. The manifolds in the parts bin don't have that top collar to install the connecting tube between both. Is that needed to run ?
Quote from: Tropic-al on December 10, 2025, 08:35:26 PMThe manifolds in the parts bin don't have that top collar to install the connecting tube between both. Is that needed to run ?
The manifolds in the photos above are RZ type and have a port on top to accommodate a crossover tube (or boost bottle), which is a common performance upgrade.
Stock RD400 manifolds do not have the port. It is not required.
Thank you SoCal for the advice. Just learning from all of you. Hopefully I will get it running soon.
Hi all. I'm back at it after Holidays, family visits, etc. Think I have everything to start it. One nagging question is what do I disconnect and/or plug at carburetors to not use the auto lube pump and run with pre mix ?? Pump is installed where it goes with no cables or hoses leading to it as of now. Will it spin and seize as there is no oil to it ?
Later on after everything is running smoothly i will connect the auto lube system.
Hope this is not a too confusing request.
Why are you wanting to remove or bypass the pump? You're going to create more work for yourself (and likely more headaches down the road) than just hooking it up and running it.
Oil tank hose (tank to pump) 90445-09122-00
Oil feed hose (pump to carbs) 90445-05M07-00 One package will do both sides on a RD400 if the tank is in the stock location.
Bleed the pump with the screw on the side of the pump housing. When no more bubbles appear you're done.
Here's where the pump distribution lines connect. (I reused the pics from 2steve's previous post to illustrate the location of the oil lines on the carb bodies.)
Right side
RD400carb_oilR.jpg
Left side
RD400carb_oilL.jpg
Plus one. Premix on the street sucks.
To answer the question about having the pump spin with no oil going to it, I wouldn't do that. You can take the plastic gear off the inside of the side cover so it won't spin.
if you read back, he wants to run premix as a test before relying on the pump.
heres what you can do.. and its easy. don't hook up the pulley cable at the oil pump.. just let the pump run at min stroke. thats going to be almost nothing oil wise. but it also keeps the pump lubricated and it will bleed it out when you're test running. then after the 1st tank, hook the pump up and set it and youre golden. I know some guys that used to race triples would run the pump just to lubricate the main bearings , have the pump set to a very minimal static setting, then run premix in the fuel. different system but it absolutely works.
:twocents:
:cheers:
Thank you SoCal for your concern and advise, it's well taken.
Like m says, since I mounted the RD400 motor on a FZ600 frame, I still have to find an oil reservoir and a mounting place for it. Have a few ideas. Before I spend $ on anything else I would like to see the motor start, run and shift as it should. Somebody else rebuilt it and has never been started. Hence the premix as a first step. Hopefully everything will go well and then I'll hook up the pump.
Another thing i noticed is the fittings where the oil feed hoses (circled in red in SoCals picture) attach to the carbs are crushed. Can I get those with the lines from pump to carbs from a vendor?
Hopefully I can get someone to help with posting some pictures. It would be a lot easier to explain my needs and work done. Thanks again to all for your input.
The oil nozzles (https://www.economycycle.com/product/injector-nozzle-rd250350400-carb-oil-injector-nozzle/) on the carb bodies are no longer available, however Economy Cycle sells reproductions.
The hose for pump to carbs (https://www.economycycle.com/product/yamah-oil-pump-line-pump-to-carbs-90445-05m07-00/) is still available from Yamaha. In my previous reply I gave you the part number. One pack is enough to do both sides. Economy Cycle carries that as well.
The hose clips (https://www.economycycle.com/product/yamaha-rd350400250-oil-line-clamp-sold-each/) used at both ends of the distribution hoses from the pump are also available from Economy.
The supply hose from tank to pump (90445-09122-00) is also still available, and if I remember right it's about 700mm (27.5") long so depending where you mount your oil tank it may work.
EDIT: just measured a new one from my inventory to be certain on length and my earlier statement was about right, and it's closer to 27.7"
as far as posting pictures... write your reply. hit 'preview' and at the bottom you then have a bar where where you can drag and drop files. thats the easiest way.
its supposed to show up when typing a reply but.. some glitch. see here:
Thanks again SoCal for the helpfull information. It definitely helps me in the process.
I'll try the posting pictures idea. We'll see how that goes !! :umm:
Hi everyone again. I finally go the bike titled in FL with the help of Bud in Vintage Motor Titles. Before his involvement it was the biggest pain in the arse. Basically impossible to do in FL if the bike came from another state with no title. If anyone needs a title let me know Ill be happy to post his web site.
Now I can spend some money in geting it running. :clap: :clap:
I have a couple of questions. Needing the carb kits, do you guys recommend any brand in particular or is Economy Cycles a good spot for any parts ? My motor is stock with air pods and RD mufflers. What main and pilot should I use ? They have a 25 pilot and can't read the main. What about needle height ?
Any help is greatly appreciated.
By the way m, I'm trying to post pictures but with my phone as I don't have pictures in my computer. Thanks for the explanation above.
When you say pod filters, if you are referring to the ones with a hard flat surface as a cap across from the carb inlet then lose them.
as far as carb 'kits' do not use the jets, or needles. the float valve and gaskets are ok. the rest, pitch
Hello again, Still in help on carburators information. On my 76 RD400, the carbs have a 25 pilot jets and an unreadable number on the main jets. One of the carb main nozzle, where the main jet screws into, has the threaded part a little buggered up that the jet won't screw into. It has 175 stamped on it. Are these numbers the correct ones and where could I buy an emulsion tube ? That's what I've always called that nozzle.
Thanks for any advice. :umm:
Do you have a manual? I never start into a new project without 1 for easy reference on stuff like this.
:twocents:
I know the numbers can be hard to read on jets and I would suggest if you haven't got one already, get a magnifying glass. I used to try to wing it without and I finally gave up last year, what a difference it makes to have one. Mine is just a cheap hand held with two optics lens and a led lamp that really helps :twocents:
https://www.nichecycle.com/categories/carburetor/mikuni-parts-by-category.html
175 is the series type of the nozzle. There should also be a size of P-2 stamped on it too. That is the stock size for a 400 carb. Main jets should have a number on them too, if not, get some that do. About a 120 for a completely stock bike.
Thanks to all that pitched in to help. Just to clarify your concerns and advice.
I bought a nice manual that includes 76 to 79 RD400 models. Unfortunately the only spec list I looked for at the end of the manual, only had RD400 F specs. After your reply I tried harder and found an Appendices list that included all models. So, now I have the jet sizes I need, able to read it with a well used magnifying glass. LOL!!! Still, my big problem is I need 1 of the P-2 needle jets as the threads for the main jet are messed up. I'll check Niche and Yambits as they seem to be the only ones that might have one.
If a member here would have one for sale, I would definitely buy it.
Thanks for the usual concern and advice to a new member.
Niche Cycle on eBay has the 175 series P2 needle jets. And they're located in Florida.
https://www.ebay.com/itm/162266775249
Look over the jet needles closely as well, if they're high mileage, the anodizing wears away and fueling profile changes drastically. Niche has stock 5L1 jet needles too.
https://www.ebay.com/itm/161063800187
Thanks for the reply Andrew. Niche did not have it when I contacted them but Economy Cycles got me both things. They just arrived yesterday.
Quote from: Tropic-al on April 13, 2026, 01:13:38 PMI bought a nice manual that includes 76 to 79 RD400 models. Unfortunately the only spec list I looked for at the end of the manual, only had RD400 F specs.
Sharing a few resources from my Google Drive that might be useful:
- Yamaha RD400 Workshop Manual (https://drive.google.com/file/d/0B4u2J3xOBcSyUHRQNHRWTmZpSUE/view?usp=drive_link&resourcekey=0-RJH7Ud9JZtzlwucxjvjuNw)
- Yamaha RD400 Parts Catalog (https://drive.google.com/file/d/0B4u2J3xOBcSyYjJXbVNKbmJ3WTg/view?usp=drive_link&resourcekey=0-jrr5PLyU_OpQMUjH_Cn-dw)
- Mikuni Tuning Manual (https://drive.google.com/file/d/0B4u2J3xOBcSyVjJWazB1ekY5Vzg/view?usp=sharing&resourcekey=0-69UA2CA-8ZGSOksNpH90Pw)