Nothing really too bad goes wrong with these bikes. Just check the usal stuff like steering head bearings swingarm bearings, wheels, Brake pads/ disk wear, subframe where the chain sometimes rubs, chain guides havent worn through, fork seals/ shock are dry oil free, kick start lever for wear at the knuckle, stuff like that. But a first impression can usally give you a reasonable idea to weather the bike has been looked after. But it doesnt hurt to have a good going over the whole thing. Good luck with finding a suitable 5er. Great bikes you'll never look back!