I've had my share of motorcycles. A Honda is always a good bet. They thrive on abuse, and run forever. Nonetheless, I'd hold out for a bike that looks as close to stock as possible. Hondas are pretty easy to find. When shopping for an oldie, look for one that's all stock except for stuff like fairings, crash bars, radios, and saddlebags- in short- nerd/old man stuff. That way the odds are much better that the machine wasn't messed with, or ridden hard. If a guy has gone to the trouble to put on after market headers, carbs, or a cam in the motor, then you know he's ridden the daylights out of that motor, clutch, and transmission. When it's your bike, trick it out however you like. But it's best to start with as close to a blank canvas as possible.
JWM