Is there a good way to tell the difference between the two? I can't tell. Just at idle its really noisy. I'm not sure what to do. I know if its a piston slap it needs boring and a rebuild. It has a rebuild with about 20 min. on the piston because its never been ridin ever since the rebuild. It just doesn't idle but it runs but as soon as you let off the throttle it dies. Whats the problem there also? Sorry if im not making sense. I think for the idle problem it needs a tors removal kit. Is that what I should do?