Buy KDX200 -90, what to check on the bike?

I'm just finishing up a complete teardown/rebuild of a '90 KDX. Here's some of the things I found:

Swing arm bearings -- totally shot, had to be replaced

Shock bearings -- not as bad as swing arm(probably since they're higher on the bike)

Steering stem bearings -- salvageable, but barely. Cleaned and relubed

drive axle -- leak behind front sprocket. Replaced this gasket (came with the complete moose gasket kit that was like $60)

Exhaust valves -- left and right both stripped, and right sheared off. $70

I changed tires myself -- interesting experience, but they're probably going to the dealer next time!

of course, YMMV, but this is what I found. Have fun!

Welcome to DRN Slash!
You've come to the right place for learning about the KDX and bikes in general. Do a search on Canadian Dave's site and see what you can learn about that particular year of bike, you should find some great comments about each year group of the KDX. The bottom line when purchasing a used bike (there's a whole lot of traffic out there in the "What Type Of Bike Should I Get" forum on this), is take a friend with you when you look it over. Good luck bike hunting and hope you enjoy the best woods bike on the planet!