my 2004 polaris scrambler 500 4x4 did fine on a longer trip, but after we had gone about 10 miles it felt like it was cutting out or going out of gear. I'd get it on the flat and it would be fine again for a minute, then cut out again when we climbed again. We were at elevation at the time (about 7 to 8000 ft I'd guess) so we turned around and went down the mountain and it was fine. The filter looked OK. Somebody said it was about things jiggling and oxygen at elevation?

 

If you go back again pull the air box lid off and see if it runs better. Had several customers do this when they were on trips in higher regions for short periods of time rather than go to the trouble of dropping the main jet.

 

I'll give that a stab.