I have a 1987 trailboss 250. When at idle the bike does NOT try to take off. But when i give it gas and get moving as soon as I let off the throttle its like i hit the brakes. All brakes are Not hung up... Also bike moves freely in neutral s i know that the rear is not locked up..... Is this a belt, or clutch problem???

 

Try puttin it up on jackstands to narrow the problem down. I could be in the clutches, my guess if it is, it's in the secondary.

 

I changed the belt amd had the same problem. So, it went up on jack stands and the process of elimination strted.. It ended up being that someone before me put the rear brake rotor on backward and it was binding in the brake cal..... Some people dont deserve to own tools... Ok thanks for all of the help.