Jus had an 89 GPX 250 with just on 50 thou K's.. It wasn't running to well when we bought it, but it was only $1000..
Gave it a good service and had the carbs fixed up, one float bowl had busted and fixed up the forks. $700 later it ran fine.
She did 2 trips to P.I. on it and sold it for $2200 2 years later..
They are a pretty strong motor so the K's shouldn't be a problem depending on how it was ridden. The front suspension was stuffed so we also had new seals and oil put in it. Its bloody soft too so I added some spacers to the forks and put heavier oil in it. We aslo put a smaller rear sprocket on it so it ran at lower RPM at higher speed and added a few KS to the top end... Just the thing for P.I. trips...
The only problems we had was a leaking water pump and a stretched chain.. She had to carry all the luggage you see, I was on the 7 and didn't want to be weighted down..

Dave
2010 Z1000
ex bikes
05 ZX-10R Race Bike - No.77
95 ZXR750R M Race Bike - No. 75
98 ZX9R Race Bike - No. 000
zx6r, zx7r, GPX750, GPX500, lots of KX's.

I ride way too fast to worry about cholesterol