Frames are actually fairly weak. Look closely for any cracks or repair jobs in the frame especially near the front end
Mufflers very hung in a spot susceptible to tree stumps, rocks and ice and often got banged hard, broken off or damaged
Rear shocks has two circular ends that bushings go in to mount. These often wore thin and allowed for slop and play.
I'd say biggest issue you can't always tell is the drive shaft. The splines often wore off to the point that shaft can/ could slip and the drive shafts are very hard to come by
Other than that amazing little machines. A real blast. Restored one for my son last Christmas. Posted a thread about it on here.
Good luck, you won't regret it
Oh! The seems to sell for much cheaper in the north east as opposed to central or west