Have a 96 500, Believe it to running rich off idle. Runs okay without air filter tube and box. Hows does the tube and box affect mixture? I think it runs leaner with out it.

 

Might be time for a carb kit,could be a worn needle and seat allowing too much fuel especially if it runs better without the air box and filter.Plus not a bad idea to check the valve setting and the cam as this was in the year range for exhaust lobe problems. http://www.ebay.com/itm/Polaris-Scrambler-Sportsman-500-Moose-Racing-ATV-Carb-Carburetor-Rebuild-Kit-/181271798775?pt=Motors_ATV_Parts_Accessories&hash=item2a34a423f7&vxp=mtr

 

Thanks for reply. New carb parts is where I was heading too. been into exhaust valves, cam was ok but valves leaked when I aired it up. They were way tight. This problem didn't show until replaced leaking/cracked carb adapter. I finding Polaris work can be a little quirky. Some are shying away from it. So here I am.