I Have a 2010 Sportsman 800 and as soon as it gets warm/Hot not overheating hot but run temp hot, it starts I Would say miss firing but i Just put new plugs in it...Anyone know what the problem could be?? Its all clean..oil/airfilter/all the basic stuff,I had a dealer tell me its probably the mass air flow sensor plug?? sound right to anyone??

 

Check the wiring along side the frame going to sensor, I believe the Brown one is the one you are looking for any damage. I had similar problem on '07 800 X2, found Brown wire to be the problem.

 

seems like it would miss even w/ it cold if it were MA sensor as well? maybe check the t-b wire harness for issues as well maybe by moving the wire when it's acting up to see if it changes just an idea.