Sled is my son's and its performance is questionable. Wondering if anyone has any suggestions as to how it should be set up? Motor runs great, just no performance and top speed is about 75 mph according to its speedo. I'm not sure what the current set up is (springs, cam, wieghts), but the gears are 39-21. I will be checking it later this week, but was hoping for some reccomendations as to what it should have.