My motorcycle has had a strange problem with the idle for a few years now. I have not been able to diagnose it and I'm hoping that someone here might be able to help. It starts fine and will run fine while driving. seems to have lots of power and very responsive. it will idle just great at 2000rpm, but once the revs drop below 1500rpm at some point it's like one cylinder stops firing completely, the engine will drop from 1200rpm to 500 instantly, the sound changes noticeably and if I don't hit the gas it'll stall out after running like that for 5 to 10 seconds. Also while warming the bike up before rides the exhaust pipe on cylinder 4 would take much longer then the others to heat up (even when the bike has been idling at 2000+ rpm the whole time)
I've tried cleaning out the carbs a couple times, this winter I went through closely and them made sure to clean every little passage and jet. I've tried switching the ignition coils and spark plugs, same cylinder stayed cold.
really starting to run out of things to try.