[Marc C]

I use my 500 to pull a trail mower and had been having problems with it running rough. Took it to the shop twice, first where the fuel pump and spark plug were replaced, then secondly the carb was rebuilt and the fuel valve replaced--that was in April '22. It sat for awhile waiting for mowing season to start. Did so, with no problems, twice. On the third outing it started acting up, and since then won't run without lots of backfiring. I replaced the air filter, sleeve (dirty but not excessively so), and spark plug, but saw no change. I use no ethanol gas, btw. From the time it went into the shop in April until now, mid-August, I'd put only 4.9 hours on it.

I suspect the carb is fubar, but as I'm not an engine mechanic by any stretch, I don't know if it needs to be replaced (which I think I can do after watching a bunch of videos) or just some adjustments need to be made.

Open to diagnostics, ideas, and advice!

 

[JKS]

Hi, I have a 2001 sportsman 500 ho that was backfiring bad also and found it was a lobe on the cam that had run down to nothing. New cam fixed it right up.

 

[Marc C]

As one who is wholly ignorant of engine mechanics, could you post an image, or a link to this part? I googled it and I think I know what you're referring to, but I'd rather not guess.

Thanks!

 

[JKS]

I’m sorry, I don’t have any pictures or a link to the cam shaft. I had a buddy of mine help me repair mine and I believe it was the exhaust lobe was worn all the way down. Mine would back fire really bad. Maybe call the shop you had it into and ask them about it or just google camshaft for your year sportsman.