horrible noise

[trxxxx]

need help I have a horrible noise coming out of the left side cover when i ride chain is ok.the sound starts when the quad warms up and you ride for about 15 min I have a stock 2005 trx400ex

[n811]

Does it do it when it idles? Or when revving. I'm sure you checked all of the obvious like oil...

[trxxxx]

Only does it when revving through the gears riding not idle oil is thin used some cheap oil so im doing a oil change right now to see if it helps