help with my Xj650 1981

hello everyone, i just got my 1981 xj650 last year, i got the carbs professionally cleaned back in September last year and i stored the bike and winterized it properly, my bike started fine however its running rich and backfires and stalls every time i come to a stop. i couldn't restart it since. i put new spark plugs, new oil and i am not sure if i might need carb cleaning again because i only drove 500km since i got them cleaned. the bike has 3500km on it. i know the friction plates needs to be changed. does anyone might have an idea of what it could cause it? also when i have the choke on it doesn't idle high.

 

What do you mean by winterized properly?

 

changed the spark plugs, warm garage and charged the battery, cleaned the tank, etc.

 

If it is ruuning rich, did you try to colour tune it. Gunson colour tune kit.

 

no i didn't, the mechanic said he tried his best to tune the carbs to make it not run rich, but the bike still does! ill check out the color tune kit, thanks for the suggestion!

 

All has to be without air leak from air box to end of the pipe. If there is any leaks - it throws out the sync.

 

He checked for leaks, there was nothing! He changed the petcock and plugged the vacuum. It also stays at high rpms delay when I pull on the throttle. Unfortunately not many people here know much about this bike. I live in a small city with 5 mechanics

 

hello. i see this thread is from 2022, but is the only one i can find (albeit minimal searching here) that comes close to what i'm experiencing. I have a 1981 XJ650 Maxim. Regardless of what I do, it always runs extremely rich, fouling plugs, no acceleration, and inconsistent idle. Here's what i've done to date. Carb cleaning and rebuild. New top end, including valve seat cutting and valve refacing. compression at 137 psi. Leak down test at 90 psi loses 2 lbs or less across all cylinders. smoke test reveals no leaks in intake manifolds or between cylinders. I've also rejetted from the standard 110 main jet down to 105, 102, 100, 95. every time i remove the plugs they're sooty and black. when i remove the carbs, there's excess fuel on the inside of the manifold. ignition frequency and intensity have also been checked and verified as good.

At this point, i'm at a loss. Any ideas or directions this group can provide is appreciated.

 

Who's jets are you using?

 

the one's that came in the build kit. after that, i've tried AB and Keihin. i know they don't measure the same (keihin 110 measured at 1.05 mm based on my gauges, for example).