I just got a 1997 Sportsman 500. I have been going through it and discovered someone put a Mikuni BST 40mm carburetor on it. From what I understand, Polaris went from the 34mm to 40mm carb in 2001 with the 500 HO engine. The ATV seemed to idle ok and do good until about half throttle. From half to wide-open throttle, it would bog down. The carb has a 152.5 main jet. I can’t tell what the idle jet is. Everything else on the machine is stock as best I can tell.

My question is: Can i rejet the 40mm carb to work with the 500 engine (not HO)? Should I just use the same stock jet sizes from the 34mm or do I need to compensate since the opening is bigger (40mm Vs 34mm)?

I’m at 869 feet elevation.