My motor has started making a very loud squealing noise as soon as the piston begins to move. It goes away once the motor is up to speed and is less noticeable but still there once it warms up completely. My clutch is not slipping or rubbing the cover. It sounds no different with the cover off, or with the clutch engaged or disengaged, it's only related to motor speed. It's at its loudest when the motor is being turned by the bike just before it fires up. Help!