I do not know much about motorcycles so please help without insult. I´m thinking of purchasing a ´83 Nighthawk 650. I have looked at it and rode it a few times. Everything seems to work fairly well but if you put the choke all the way down and let the idle drop to like 500 rpm the engine starts knocking (ticking or however you want to describe it). It only does this near 500 rpm and disappears when you raise the engine speed. Is this just due to running it at too low of rpm or is this a problem/future problem? Also if it has 24,000 miles on it and very few other problems, how much is it worth?