I have the same problem with my king quad now. Last september i was riding with my kids and would never get over 45 on the trails, but when i got to a road where i can open it up i cant get over 50 mph. It starts getting terribly hot also. Does anybody have and idea what might be causing that? I checked my filter clean batter is low , but put my daughters batter in it out of her eiger and it still wouldnt get over 50mph. Please help im going nuts:aargh: