I am trying to help a friend of our boys get his 80 NC50 running and it does not want to run above 15 mph. I took the pipe off and that did not help very much. The carb is clean throughout, the air screw is set at 1 1/2 turns out and it has a new air cleaner element. It also has a new plug. Does anyone know what the compression is supposed to be. Perhaps it may new a new ring job?