RD400 get in touch w/ me dude, i'll hook you up
A couple of questions:
1. Does the problem come and go at specific throttle positions? (if so it is carb related and i can help w/ jetting..jetting with DG's, FPPs, spec II, pro-flos, stock pipes.
2. Are the carbs stock or have you changed from the stock type needle jets (175 - P2) to primary types (169-P2).
3. airjets removed or stock?
4.stock airbox or aftermarket? specifiy pods, RD350 boot, etc.
5. What is the timing set at? Chambers? 1.8 - 2.0 mm BTDC
6. What size pilot jets?
7. airscrew settings (how many turns out from stock)
8. Ignition. Is it stock or aftermarket like Newtronics.
There's alot more, but if you trailer the bike down, we could look at the bike and i could help you jet. I'm more proficient jetting pipes like Factory Pipes, Spec II, DG's, Pro-Flo's.
send me an e-mail. I have
This is what my bike is running (1976 RD400C) ON PREMIX @32:1, but i can jet for the injector/stock carbs also!!
Carbs: VM28SC (if your carb internals are stock, this doesn't apply and you'll probably be running 4 sizes larger mains, 1-2 sizes larger pilots than stock)
WARNING: i have modded my carbs with 169 P4 needle jets (richer than the stock 175 P2's w/ 5DP7 vice 5L1 needles on middle or 4th clip, 220 main jets (prolly 240-260 w/ stock carbs & injector, but each machine varies), running a 35 pilot and the airscrews between 1 and 1-1/4 turns out.
I removed the airjets and pretty much turned them into R5C/race carbs, putting a 2.0 airjet in (has to be drilled out, then a 4mm tap w/ .7 pitch to thread in the new airjet, the plus side is that you can buy the stock .7mm airjet and thread in, if you aren't satisfied with the 2.0 or want to return to stock....look up sudco/mikuni to order the catalog with the parts numbers.
Filtration: RD350 boot with tall K&N filter...you can buy that setup from spec II, motocarrera or Pro-flo ( got some kicking chambers that you would like and cheapest of the bunch)...you should come check them out in person)
I have the newtronic / pirhana ignition (optical trigger), time once and forget (3 year warranty...i have had mine about 3 years and no problems). about 160 dollars from www.motocarrera.com. 1.8- 2.0 mm BTDC...i have the dial indicator (100.00 dollars) and the zenon strobe to time it right and with the engine running. we align the marks on the gen cover and then time running around 5k rpm...have large fan for coolling while stationary.
VW Bosch Super Blue coils, you can eliminate the ballast resistor and wire straight in, then you have to mount them on the front downtubes. Spec II sells coils that mount under the tank in the stock location www.spec2.com.
USE only OEM stock head / base gaskets...Vesrah is sh*t and leaks. Torqueing sequnce is critical and do in an "X" pattern. I slowly torque from 5, 10, 15, 17, 20 to 22 ft-lbs of torque on the heads...it take 4 to 5 heat cycles for them to hold a torque setting. first torque ride EASY, fully warm engine, let cool with industrial fan in front of bike for about an hour, retorque...this will have to be done about 5 times for the NEW head and base gaskets to hold torque.
I'm the man around here when it comes to jetting/ timing these things. If you plan to run HARD, i'd play it safe with a B9ES plug, but if you normally ride easy the stock plug should be fine.
I also have a spare rectifier/regulator....i MIGHT be tempted to sell, if you have a problem there, but it sounds like its probably jetting related....the key is the problem comes and goes acoording to throttle position.....this will also tell you what part of the circuit the carbs are having a problem at....tape off the throttle in 5 even increments with masking tape....0, 1/4, 1/2, 3/4, WFO throttle...if it comes and goes at a specific position, it's carb related....don't pay attention to rpm's
if the engine falls flat, dies or makes no power but reves.......your probably lean....i suspect this is your problem.
No worries I can help you.
I have a trick for helping rid yourself of the 5k flat spot.
RD400man
PM me
