I have an 02' 660 Grizzly, and recently it has started making a rapping sound in the engine. It is definitly not a valve tapping. I just had them adjusted and the mecahnic said that was not the noise. They want 500 bucks just to tear into it and tell me what it is. The mechanic said he would not worry about it and just ride it keeping an ear out in case it gets louder. I have great power and it does not smoke any. I have had people tell me it could be a wrist pin or a cracked piston. It does get louder when under power, and does seem to be directly related to RPM. Have any of you with a Raptor or Grizzly had this problem? I welcome any and all opinions. Thanks!

 

you could be running to lean?

 

It sounds like the same problem I am having. Not sure what it is.

 

could it be a crank bearing?

 

No It sounds like valves chattering with bad gas and not out of adjustment or timing off.

 

could be due to a small pin shearing in the oil pump. your problem sounds just like mine, and that was the problem i have.