Went riding yesterday and sled started out running pretty well. As we went higher in elevation it started acting rich. Pulled the plugs and put in new ones rode back to the pickup. When we got back to my buddies shop we pulled the plugs again and they showed it was lean. Used a scope to look at the pistons. They both looked the same. Both had some pitting around the edge. Checked the compression clutch side was 130psi and mag side was 145psi. Was riding a couple thousand feet higher then normal. Need some suggestions on how to diagnose.
