My wife's '87 1200 belt-drive Sporty has developed a squeak in the rear drive/wheel upon acceleration, immediately from startup. Not to be confused w/ squeak upon deceleration (usually belt adjustment). No squeak when bike is on lift and wheel spinning free.
The drive belt is adjusted and running freely. Could this be a wheel bearing problem?

 

Could be the back brake pads draging. For some reason on my shovel, when the weight is on the back tire the pads squeak.

 

Thanks,
Will check tomorrow.
If you touch the brake when squeaking, does the squeak disappear?

 

Checked brake pads, not the problem. Squeak coming from secondary drive. Starts immediately upon acceleration, stops immediately when throttle is released. Drive pulley is tight, maybe belt too loose?