2001 sprortsman 500 no start back fires
 

Hi everyone, im brand new to this forum, as a matter of fact ANY forum! well here goes. i inherited a 2001 500 h.o. sporstman i helped a friend and he gave it to me(im an auto mechanic 27 yrs.) he was riding it in the snow doing donuts machine just shut off and wouldnt start from that poin, he read a forum that stated the cams go bad he started tearing down and lost interest and 4 yrs later welhah!!! im here, ive cleaned the carb,tank and all fuel line,new spark plug,new pet cock(old one broke) cleaned flywheel and pick up senser, checked time dead on,adjusted valves that were not out of adjustment! and here we are weeks later she cranks backfires thru the exhaust,(it did start and run for a little while but not long) any one with suggestions wopuld be greatly apprieciated! and i promise when i fix this i will repost the fix(not like 20 thousand other posts that no one puts what the fix was)

Welcome to the forums. First off if it's a 2001 model Sportsman 500 it should have HO on the decals and would have the updated stronger cam and larger 40mm carb. If it's a 2000 model then possible it may have a ground down exhaust cam lobe. Doesn't have to be all the way flattened to cause problems,but symptoms of the worst ones are will idle but wouldn't take throttle and would back fire through the carb/exhaust. Both intake and exhaust lobe heights should be between 1.2884-1.2924 with service limit of 1.2766 that you can first check out to see if it's a cam related problem.

If its not the cam it could be a dirty pulse coil. Mine was hard to start and had the odd back fire , it turned out the magnetic pulse coil face pick up all kinds of metal filling from crud getting down the pull rope hole.