You're talking about the sheaves on the drive clutch (motor clutch)? You're saying that when you are in FWD the sheaves comes together and the belt rises in the clutch as rpms increases; but when in reverse, the sheaves do not move in on the belt at all and the belt just hangs there? The motor only spins one way (CCW) whether you're in FWD or REV so I'm trying to figure out why it would only spool up in FWD. Can you move the driven clutch (axle clutch) by hand when in either FWD or REV?
Does your drive clutch look like this?
