HAD MY RAPTOR OUT TODAY AND NOTICED THIS NOISE PROGRESSIVLY GETTING LOUDER. IT SEEMS TO BE COMMING FROM INSIDE THE CASES, UNDER THE REAR PORTION OF THE STARTER. WHEN CHECKING MY OIL I NOTICED THAT I WAS ABOUT 1/2 TOO MUCH. IT DOES'T SMOKE, AND IS AS FAST AS IT EVER WAS. EVERYTHING FEELS THE SAME. JUST A TINNY KIND OF KNOCKING SOUND (NOT DEEP AT ALL). SOUNDS LIKE SOMETHING BANGING AGAINST A HOLLOW PIECE OF METAL (BUT FAST). DOES ANYONE KNOW WHAT THIS MIGHT BE. FOR THOSE WHO HAVE HAD TO HAVE THEIR ENGINES REBUILT, HOW DO YOU KNOW YOU NEEDED IT DONE.

 

http://216.37.204.203/Yamaha_OEM/Yam...A=182&B=32
http://216.37.204.203/Yamaha_OEM/Yam...A=182&B=32


Open up you where you adjust your valves and look for tiny pieces of white plastic. If you find some I know what your problem is and it will be 400 bucks for parts w/o labor. Let me know.. The links are above just in case it's what I think it is.

 

Have you checked your axle and swingarm bearings for wear? When my swingarm bearings started going out, I could have swore I have major troubles similar to yours.
A loose skid plate could do that too.

 

I only hear it when it is idleing sitting still.