I have a 2005 CRF250R with a 175 main, clip on 4th, stock leak jet and fuel screw is 1 3/4 out. It was a pain to start. once i get it started it runs fine but overheats sometimes. We took the Carb off last night and re checked everything. Valves are in spec. We think it could possibly be a head gasket leak. any ideas?