So here is my deal. Yesterday while riding, At half throttle just cruising, I could hear some kind of noise coming from the left side of the engine near the cover. Not so much a knocking, or even a rattle. Just intermittently making a shake, okay, maybe a little rattle noise. NO loss of power, and I did not notice it idling or at full throttle. Maybe more like a vibration... anyway, hope someone has an idea what it could be... thanks...
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Okay, let me ask it a different way. There really isn't anything on the left side of the engine near the cover that could be slapping the case itself, I.E. timing chain or something like that is there?

 

What kind of ATV?

 

OMG I am a bonehead sometimes... 2006 Wolverine 350 less than 150 hours on it...

 

Lol. the timing chain is on the left side of the engine and could be making noise. I believe that engine has an automatic timing chain adjuster but it can only adjust so far. With low hours it's questionable that the timing chain is the problem. The valves could need adjusting but they're on the front and rear of the engine head. It never hurts to check their adjustment anyway. Also it wouldn't hurt to check the oil, verify the oil weight, and make sure the oil filter is clean.

 

Starter clucth oneway bearing is on the left side also.

 

Echoing Raptor450 above, I had a cam chain on an old XR400 stretch past the adjuster's max position, causing a pretty good rattle. A new cam chain quieted that motor down nicely.

Also, it is possible for the spring in an automatic cam-chain adjuster to break, letting the chain slack flop about. Not an expensive fix.

 

Thanks guys...