The last two times I had my machine out it is acting up. At full throttle while climbing a hill or on a straight away it takes off great then as it gets up to speed it will stutter and lose power untill I let off throtle. It idles great and runs great until its pegged. I was only abble to get it up to 45mph at one point wide open. Another time it lost power climbing a hill that my friends 400 went right up. Never had this issue before. Need some help nailing it down. any suggestions or similar issues?