i have an 89 kx250 and i just had the whole top and bottom end rebuilt by a dealer... so it would be done right... anyway, when i ride it, it sounds like there is some sort of air sound like a low hum, like wind rushing by. it does this even when in neutral and the motor is idling, it isn't loud enough to hear when it revs up though. any ideas on why this is happening and if it is a problem let me know. thanks