I bought a Yamaha XJR 1300, 4 cylinders air-cooled with carburetors.
It has a problem known from the sale (hence a very decent price), when the engine is hot, the rpm tend to stay higher than the idle setting after a throttle blip. I felt confident I could fix this easily but I am still struggling. I already tried some basic things, replacing the admission pipes (they were cracked), adjusting the TB sync (it was way off), checking for any obvious malfunctionning of the starter. Basic maintenance was done (oil+filter change, air filter, spark plugs).
The problem was greatly reduced by the TB sync (like 80%) but is still present, on a standard ride from home to work I have to lower the idle screw some 2 turns to have an acceptable idle when hot.
It is not only a idle setting problem but really a great difference between idle and RPM after a blip, and I feel a strong lack of engine braking when cutting gas at low to mid rpm.
Next thing I will try will be to disassemble the carbs ramp to set everything to stock settings if needed (idle mixture, needles).
One more thing, it sounds like it has a tappet clearance problem as it does a very clear ticking sound on the left side of the engine head. Can it be linked to an admission missbehaving?
I will take any advice on what to check/set to fix this, thanks in advance.
Update : I think I got a strong lead, I removed the carbs ramp and the two right carbs have a power valve spring too weak, they are very slow to go back in place after I push them up. The rightmost one even stay half-way and makes a metalic tinkle when I push it. So I'm going to buy 4 new springs and hope this fixes the problem.