I have an 2002 Polaris Sportsman 500ho. I recently had the original carb rebuilt after the person I bought it from put on a aftermarket carb on and I began having issues of it wanting to stall and choke itself out after a long ride or when it was hot. When I got it back from a reputable mechanic and put it on to start and test and the idling was great. When I pushed the throttle to rev it started coughing and spitting a small spray of fuel. When I pushed throttle all the way it would slowly, but surely clear up. What I would call the midrange seemed to be the issue. This was without the airbox or anything on. I proceeded to put it all back together and go for a test ride and it still is coughing and what seems to be a backfire type event. It has little to no power as well. I checked the plug and it showed a clean burn. I'm not sure where to go from here and the mechanic is puzzled as he went thoroughly through the carb. He's done hundreds of these rebuilds and even did my scrambler last year that runs perfect now. I've read so many possibilities during my research that it mind boggling. I was hoping for some insight before I took it all apart and had him go through it again. Thanks

 

Tl/dr check your timing chain and reset it to tdc and reset your tensioner.

Ive got a bayou thats been a real head scratcher. I had it working properly once and that was right after i removed the head and set the valves. When i put everything back together it took a moment to get it started i released the timing chain tensioner and cranked the engine. It then started and ran didnt bog down for about 20 minutes. Then and ever since it bogs under throttle. I thought it was timing related (i still do ) bit everyone else who has more experience with small engines pointed to fuel so i bought a new carb replaced jets tinkered and adjusted.i was able to get moving under 1/4 throttle. Now im sure its my timing chain and it may be worth a look to have your guy reset your timing chain too. Wouldnt hurt.

 

Wow! I didn't have an issue before so I'm not sure why the timing would be off, but I'll check into it. Thanks

 

Sorry for the wall o text that's why I put the tldr first. Chains stretch, give it a shot if nothing else you've eliminated something easy.

 

Did that fix the problem?