I have a (1 year old) 70 Yamaha that cuts back to 1/2 throttle when I try to go. Changed plugs, gas , gas line , fuel filter. Still same problem, but started fine and ran fine till you raise throtle.
They first said probably water in gas. Took it in and they changed plugs, pulled the carbs, compression test, and finally said air leak in the gas line. They redid my gas line conectors and charged me over 200 bucks! Took it home and it was hard to start and still won't take the throttle! I think it's fuel pump or electronics. Before I take it back to the shop, any suggestions?