Just got my self a '81 XJ650 and in need of some help.

I recently purchased a fully stock '81 XJ650 with 22k miles from a private seller off craigslist. I am so surprised as to how well these bikes performed given it's age. The bike starts right up with some choke, idles at around 1100rpm after few minutes however, after the engine is hot the idle sticks around 2,000 and slowly makes its way down to 1500 if you nudge the throttle. The idle speed adjustment didn't do much to help.

My first suspicion was air leak, the intake boots looks cracked but not too bad. I pulled the carbs for inspection and clean up. Everything looked clean. It looked like PO used RTV to seal the boots to the head, which I think is the source of the leak. I pulled them off and cut out new gaskets for them, and sealed all surface cracks with RTV. I also got new vacuum plugs. After I put everything back together, it idle perfect, but the bike runs like crap! It sputters and takes few seconds for the power to kick in and lots of popping noise on deceleration. I checked the mixture screws and they were about 3.5 turns out. I believe the PO tried to make it run rich to compensate for the air leak. I also noticed the exhaust 2 & 3 are very hot and 4 not too hot but 1 not hot at all.

My plan is to:
1. check valve clearance
2. re-inspect/clean the carbs more thoroughly
3. vacuum sync
4. color tune

If anyone can give me their opinion on my situation I would highly appreciate it

 

Omg I am so stupid. I thought the main jet and pilot jet were the same thing, I must have switched them when re-assembly.

 

lol.... I did the same thing, but it took me over a month to find it....

 

It indeed was the problem. I put them in the right place, 110 in the main and 40 in the pilot and also bench synced. Now it purrs like a kitten and the high idle problem is gone!

 

easy overlook.