As the title indicates my 97 Explorer 500 4x4 is sick. It will run good until half throttle and then it backfires through the air filter. If you are patient you can get it take more throttle, but you have to really work. I am about to take it to the local Polaris dealer. The shop said it would be either the carb or the camshaft. Any info. that might help me. Thanks.
Oh, by the say, I have only owned it about 6 months... it was doing this just a little when I bought it, but it has gotten worse.

 

as you mention it getting worst its probablly the exhaust lobe on the cam... polaris 500 engines have been known to wear them flat