Yamaha rd400 jetting

[old-too-smoker]

Gentlemen,
My RD400F is making a lot of progress, from boxes of parts to a fairly complete motorcycle.  The RD400F original carbs are on ebay if anyone is interested. I have decided to use a set of RD400E carbs I found in the boxes, Unbelievable I found every piece! prev owner likes to dis-assemble everything and never put it back together. Will need a bowl gasket set and a new set of float valves. I pulled out all the jets which came out fairly easy, even the pilot jets. There is some corrosion near where the main jet goes on lefty, but I dont think it will be an issue, any opinions? Looking around online the 400CDE jet needle and needle seem to have different values? Mine are 5L-1 and 75P-2, I am guessing they are stock sizes but cant verify that, anyone know? I have stock pipes with a K&N Y-boot, first pass thinking of 27.5 pilot with 145 main.  Looks like I can add a cross over pipe with these manifolds, worth doing?

[SoCal250]

I swapped out the 2V0 carbs on my RD400F about 5 yrs ago for some 1A1 units. Best mod I have done! I just sold my 2V0 carbs on Ebay last week.

I think your carb body should work OK since the corrosion in your photo is all on the outside of the main jet area. With that much corrosion I would get new jets, float valves, etc so you're starting with fresh brass parts. 5L1 and 175 P-2 are stock and same as what I am running.  Jets and carb bowl gaskets are available from Economy. And obviously you will need a new throttle cable, which is still available from Yamaha (1A0-26260-00-00). Economy has that too.

I ordered a bunch of jets and then used the jetting procedure here: THE TECH LIBRARY »CARBURETOR - FUEL/AIR DELIVERY

[old-too-smoker]

Thanks SoCal, already ordered all new jets, even the needles and jet needles, float valves etc, all original Mikuni parts, and not the cheap stuff! Here is a RS250 carb from a project bike I bought on ebay, rest of the bike was like new....

[SUPERTUNE]

Never use any old jetting parts if restoring these old 45+ year old carbs.
Re-use slides, floats, float pins and choke lever assembly if not too bad.
The 5L1 stock needle are usually fine if not bent or any of the hard anodizing worn off.
Replace needle jets, main jets, main jet washers, pilot jets, and needle & seat valves with a bowl gasket.
Sometimes you have to replace the o-ring on the idle screw and the air mixture screw.

Now that I hate the time it takes to make old fussy 45+ old carbs clean up and run right...I'm more likely to just buy brand new carbs anymore as it save a lot of rebuild time and headaches, like warped leaky bowls, etc.

The new VM28's work well if jetted for the application. You will just have 2 choke levers.
Also do the raptor petcock conversion if your using any stock RD400 tank including the Daytona tank.
NO crossover tube on the stock 1/4 nipples just plug them with rubber caps.

Now if your modifying with Banshee manifolds and a crossover tube... now everything changes with jetting as you now would need to go with a modified air jet system to run primary needle jets and not bleed needle jets w/ different needle and smaller main jets as the primary conversion needs way smaller main jets to work. (190-210)
You will need to be at least a 230 & up with a 30 pilot at minimum with a Y boot air filter on bleed needle jets and restricted air bleed size.

Chuck