Rejetting VM34's

[STVR]

Hi Everyone,

SO I bought some new Mikuni VM34's got them on my bike started up first try runs pretty well except at full throttle get a little choppy I expect my mains need to be a bit bigger? Here is what I re-jetted to what are everyones thoughts on the stock needle jet with the Mikunis? Should I get a different needle jet?

Here is what was stock and what I am running:

Stock Mikuni as I bought it:
260 MAIN
35 PILOT
159 Q-2 Needle Jet
6DH4 NEEDLE
2.5 slide
2.0 air jet

This is my current Jetting:
180 MAIN
25 PILOT JET
6DH4 NEEDLE
NEEDLE CLIP IS 4th DOWN FROM THE TOP

 

[STVR]

Also I have a 1975 XS650

 

[retiredgentleman]

http://www.xs650.com/forum/showthread.php?t=43

 

[5twins]

It appears you bought the off-the-shelf "generic" VM34. It is set up rather rich for use on a two stroke dirt bike. There is a well established and tested baseline for how to set these carbs up on a 650. Your mains and pilots are in the ball park but your needle and needle jet are not. Also, it's standard practice to totally remove the air jet and run without it. All the info you need is in the link RG provided.