Its obvious that you have the wrong belt on there It is not a comet 40 series.
1)determine of you have a 20 or 30 series torque converter (20 series is symmetric sheave, 30 is asymmetric sheave) make sure the drive unit matches the driven unit (cannot mix 20 and 30 series).
2) determine the driven unit diameter (its eith er 6" or 7")
3) measure your center to center distance, the distance between the center of the engine shaft to the center of the jackshaft.
4) reference this chart and find the belt number (it is the number before the A)
https://www.gokartsupply.com/tcbelts.htm
5) buy the belt on ebay as it is cheaper, or get an authentic comet belt
6) while you wait for your belt to come, disassemble the drive unit and inspect it. The driven units dont usually have the most problems, but they can have wear tab, spring, and rust problems.
7) clean and lubricate the drive and driven units. Lubrication involves a dry moly type spray.