I have a 1980 arctic cat jag 3000 f/a 900 original miles that just developed an engine knock. You notice the knock at idle and when the engine comes up to speed. It doesnt knock when you rev up or when its coming down. The knock isnt very loud but its enough that i noticed it and have ruled out all the stupid obvious problems (loose belt protector, bolts, etc) from what i have read it sounds like its my piston rod bearings? I dont know if anyone else has dealt with this and can shed some light. I would much rather do a top end rebuild that have to tear the whole thing down. I also run my cat rich, usualy 65:1. Thank you all in advace for your advice / thoughts!!