"timing is off" sounds like some kinda excuse that the top end is shot, unless the woodruff key broke the timing cant be off, and if he pulled it apart to see the key broke he shoulda replaced it, they're only a couple bucks at the hardware store,
another good lie is the carb needs adjusted, so this sounds a little fishy to me, just be sure the rest of the bike is in good shape..tire's, plastics, bearings ect, ect, or your just buying a roller that needs tons of parts and work, may not be worth the $250 if everything needs replacing, just my 2 cents