OK so my 2007 Sportsman 500 X2 started sputtering found out I tried to adjust Idle at handlebar and was way to tight ( no play in thumb lever) after fixing that left for test drive started sputtering up hill while seating on seat , removed seat and ran good, so I removed the Air intake that goes to top of air cleaner box and runs great WTF is this bad to run without large plastic air intake or do I need to look at something else. I also checked all electrical connections and looked great. I also replaced spark plug and fuel pump.

 

it does sound like an air restriction if it runs better with out the top of the box(which you should not do) or maybe getting too rich. how did the plug look when you replaced it? if it's running too rich then it will be very black maybe wet as well.

 

Yes the first one was black but thats because it would pop and misfires but now it looks fine