Hey guys just picked up a 2005 r6 and there seems to be a rattle noise coming from the engine. It's got about 25k on it and the guy said he's never done a valve adjust. Wondering of that could be whats going on, or I was thinking timing chain. Do those chains stretch easy like make too much slop? I'm a mechanic and a valve adjust seems pretty straight forward. I've looked at some vids to see what kind of upper end system they got and it seems like there's a few different ones. Would I need to shim buckets or are there adjusters?