I picked this bike up with this pre-existing condition so I don't know how it got this way. Thought it would be an easy fix but it's really frustrating me. 1999 Polaris Sportsman 335. Will not idle for more than a few seconds, runs very rough and misses at lower rpm's. Choke/enricher has no effect at all on how the engine runs. Hot or cold it makes no difference.Starts up with no choke every time. I cleaned and put a kit in carb, changed air filter, fuel filter, new fuel pump, new plug. Replaced CDI with RM stator DC conversion, new coil. Nothing has made a bit of difference. Compression is 80psi. I even checked the cam lobes and they look good. Spark plug is sooty black within a few minutes of running. Does anybody have any ideas about what could possibly be going on with this thing? I'm about out of ideas. Bike runs terrible!

 

well 80 psi would be first issue I would say as it should be way more then that. maybe valves aren't closing all the way if they are time to look at piston/rings. good luck

 

Manual states 50-80 psi is acceptable. These engines have a compression release.

 

wow am I ever shut in the 2 stroke world lol. you think I should have known that since I owned the very same year bike. sorry about that.

 

Sounds similar to my situation with my xplorer 300, except mine will idle, just won't take throttle, falls on its face and backfires. Been thinking maybe the timing, but not sure.