last year i changed the cam on my 500 sportsman. had troubles getting it to run was popping back through the intake. finally got it to run. i was riding and it just died. after replacing needle jet, jet needle, needle valve, and diaphragm assembly. now it runs but blows gas back into the air filter and i don't know why. i checked the timing and it seems fine. thanks for any help.

 

Check valve clearance for tight valves, Timing MUST line up with cam sprocket locating pin center of head,plus index mark on crank sprocket must line up on case mark.If carb correct as you say,ONLY thing I can think of.Plus if piston worn can also cause problems.Did you pull head and check piston/ring wear also?

 

i did not pull the head. compression was about 90 psi. wot lacks power also.