Ok I have a predator 500 runs great but plastics are rough and it shows signs of being ridden. (Only paid $330 for it for I can't complain). Found a so called project on Craigslist today for a predator 500, took the drive down and he said it was knocking in the bottom end. I heard it a little at his house but it was running fine and knocked for a couple seconds. I paid 600 because it is extremely clean and wors case I swap motors and have a nice one. But he said there were metal shavings in the oil. I had it running and idleing fine no knocking. Even drove fine. I'm going to do an oil change and see what happens. Any idea of what could be the problem?