My motor runs fine at the start up and up to 3/4 throttle but starts spuddering when I go to full throttle. I have already brought it to the mechanic twice and both times I was told there was nothing wrong. I don't think the mechanic is running the motor full throttle when he checks the engin. My question is, have any of you had similar problems and can give me any advice as to what may be causing this. Thanks for any help you can give.