I’ve finally got some seat time on my 1997 Kodiak. It runs pretty good after putting in a new timing chain and tensioner and getting the carb rebuilt (it was blowing black smoke/raw gas). I set the valves and a local ATV shop then did a leak down test, it was 3% or as the mechanic said excellent, compression like a new engine. All in all, the ATV is now running really good, no smoke, but it still has a metallic-like chattering noise coming from the top end, which increases the faster you go. The mechanic said it was just the age of the engine showing and the valves are chattering, but they are set right as the leak down test was good. The noise doesn’t sound like a rod knock – going 70km/hr I’d think that there’s no way to mistake a rod knocking for a metallic chattering sound.

So my question is, can I run a heaver weight oil to try and quiet down this chattering noise?