I just started hearing this whining noise from what sounds like the crank case it's not all the time only sometimes and when it happens the bike won't rev out all the way and sometimes when you put it in first gear it dies while holding the clutch in I can't find a bottom end rebuild kit anywhere and was told hot rods is a very bad idea but when the noise goes away it will run fine just bought the bike yesterday and don't know what to do please if someone could help it would be much appreciated