I'd be interested in the ownership linage and if the proper maintence can be proven. A 20+ year old bike with tons of power is generally enjoyed ALOT. Then it get's parked until it's sold again or the owner get's their licence back. I'd size up the owner and what they tell you to help understand the history of the bike.
I'm not sure changing from an 80s Sabre to an 80s Kawi is going to help improve the maintence factor. Just might be a change in ride.
The seller could be experiencing the same thing you are with your bike.
The thing about some older bikes that MAY have been parked for awhile is, they don't accumilate too much road rash and look pretty good for their age. But, they may have been parked for a mechanical reason and didn't have the $$$ to fix. Then they cheap out and fix it the cheapest way possible to dump it.
If they've kept it plated and licenced for the road and take it out occassionally or still ride it regular, I'd feel better about it.
Anyways, I'm too far west to help out man. Good luck. I'm sure someone will jump in to help out for a wobbly pop to two.
Cheers.