Are the wheel rims actually damaged, or do they just need to be trued?
A replacement seat cover should be pretty inexpensive, maybe about $30. You might also be able to find some reasonably priced replacement plastics as well. I'd imagine that a new wiring harness from Yamaha for a bike like that wouldn't be terribly expensive either.
Both. The wheels have multiple "flat spots" at the lip, and the run-out is pretty excessive. They are also very, very rusted and pitted. The front hub is is good shape, and the rear is usable. I'm still weighing my options on good used wheels, or replacement hoops.
I suggested a $35 Moose racing seat cover when I saw the roll of blue duct tape come out. The motion didn't carry.
It doesn't look like any of the regular manufacturers (Acerbis, Maier, UFO) have plastics available, and for the most part they're not to terribly expensive from Yamaha.
The harness is out of production, but the one that I have is repairable, but the battery cables are another story...
All in all, this thing is a basket case, but it's solid. Mostly, it's going to need 17 years of maintenance and repair. The carb has a hole worn in the diaphragm cover, the chain slider is missing off the swing arm, and a dozen other little things.
It won't get fixed over night, but it will keep me occupied until it warms up again.