I recently bought my first bike, a 2000 KX250. Because i am a short guy, around 5'6 and 150 lbs, i loosened the nut on the rear spring almost all the way so all the tension was out of the spring to lower the bike. I noticed that when i am going full out or close to full out the rear end is really rough and vibrates quite bad. is this because of the suspension or could it be that the rear wheel was not put on right.?