Yami

I'm looking for advice and a service manual for a 1990 Yamaha 250 Moto. Its old but its mint except for a pretty bad driveline noise when changing from forward to reverse and back. It also makes the same noise if you are moving forward at slow speed and you bounce on the suspension. I think it could be the drive shaft U joint. Any advice or help with a service manual would be appreciated. Under the gun for timing. Taking it up north in a week and a half.:canadaflag: