Kickback and carbs spitting vm34


XS650 Member
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San Jose CA
Hi guys! I've been getting some mean kickback and the carbs are spitting fuel when I try to kick start it. I found that if I flip on the choke, it'll kick back and spit fuel out the carbs almost every single time when kickstarting , but right after flipping off the choke, it'll start up in one or two kicks with little to no kickback and no carb spitting. I've already checked the timing and it's right on the marks, maybe even a bit retarded. Valve clearance is good. I'm running hugh's complete cdi system so cam chain tension can't be the problem. Cleaned and synced the carbs. Float levels are good. Plugs are black and smell like fuel. I'm guessing either there's something wrong with my float needles or my idle circuit is way too rich and flipping the choke on overflows the carbs?? I am at my wits end and would like some direction.

kickstart only with capacitor
vm34 carbs
Pilot jet - 17.5
Main Jet - 165
6f9 needle
159 P-5 needle jet
2.0 slides
It started after I got the bike from the PO. Seemed fine when I first got the bike but the PO messed with the floats somehow before I got the bike cause the left carb was overflowing. The bike rode fine but started having these symptoms about a day after I first got the bike. Both carbs do it but I think the left spits more fuel. I haven't pulled the choke plungers I'm planning to take apart the carbs again tomorrow and take a closer look. I thought the jets were small too but I figured out that 2.0 slides run richer than 2.5 slides.
yeah I’m gonna take em apart and check the float levels again. Anything else you can think of that could be causing these symptoms?
Drop the float bowls while the carbs are mounted. Gently lift each float and turn on your fuel petcock. No fuel should flow. If fuel flows your needle and seat may be dirty or worn. After that check, go ahead and remove carb to set the float height. I have VM34s on a stock XS650 motor with Unis, 1.5" headpipes and Commando muffs. I have 180 mains, 15 pilots. I knew the needle but can't figure where I recorded it. Forget what the slides are. Bike runs pretty damn good. I seek a second opinion from anybody who wants to ride it. The carbs were purchased by PO from MikesXS AFAIK.
I have ridden the bike before with these symptoms. It rides fine, just getting it started is a pain. It will kickback on choke every single time but starts up with no choke. Could the needle and seat still be the issue even though it runs and rides fine after kickstarting?
I am not versed enough to know. A needle and seat that dribbles a little could overfill the bowl. But that spitting may indicate a higher fuel level in the bowl. Easy enough to do both checks if you are verifying float level anyway. Do you have vacuum petcock(s)? Do you turn your petcocks off when not running?
Float height looks good, dropped the bowls with carb still mounted lifted up the float valve and turned on petcock fuel was not flowing, and floats are still good. Now im thinking it could be the size of my inlet needle assembly, its a 3.3 not the usual 3.0. Any thoughts?