Just finished rebuilding the engine and the powerband is all weird, like I have to have it pretty much wide open before thers any sort of hit, and just the other weekend the power was there right away. My dad was riding it and he couldnt keep the wheel on the ground in any gear and now this weekend its acting all weird. What do you guys think it is, also just changed the spark plug went with a different namebrand and the spark plug seemed shorter, just wondering if that would make a difference, or if its the carb setting. Any help would be great thx! The bikes a 1983 yz80