Hi, I am having a problem with my wheeler. It's a '99 450 ES. You have to press the throttle really far to get it to move and then it moves very slowly even in 1st gear. Related to this problem is the fact that when I push the wheeler slowly in neutral the back end goes up and down, up and down, over and over. It is a feeling almost as if the right rear wheel was taller than the left (which is not the case). Could this be a bad rear axle? Any other suggestions? Thanks!