If I were you I would tear it down for an inspection. Unless it has been changed your
clutch should be a Primo/Riveria pro clutch. The clutches for that year were a 2 piece
basket and starter ring gear, with the starter ring gear bolted to the basket. The bolts
are known to break or come loose from the basket, which starts out with slipping
in high gear, then when all are either broken or completly loose the starter will not
engage the ring gear, and the broken bolts start to tear the inter and outer
primary cases up. You will need to pull the clutch basket out to inspect. Riveria's
web site has some good pictures and details on tear down and install.
Good Luck.