For any used bike check sterring head bearings,fork seals,chain/sprockets,tires, feel what the rear shock looks like,see if there are service records(I have mine since it was new in 98)check for signs of rust in the nooks and crannies, sound of motor,boogered up bolts and nuts.Even a compression check on older bikes.
Then you know what you have to put into it if you deside to purchase it.