I have a SCR500 that came down with a little case of knock-i-tis, gave the machine a complete tear down and came up empty handed, piston to cylinder is perfect, wrist pin is perfect, main roller bearing also has a perfect fit/ and i also checked out the gears, no abnormal wear or witness marks anywhere. Iv'e taken it to three different shops to take a listen to it, the noise seems to originating from around the oil pump area, so I was wondering if anybody else has had a knocking oil pump or a knock in that area? Seems to me the only thing I can do is ride it and listen very carefully for it to get worse then maybe it can be found, at least thats what the final shop I took it to suggested, as bad as it sounds thats all im left with right now.
HOPING FOR HELP!!!!

 

What year model?.... It 97's aren't counterbalanced and they have a pronounced "knock" to them at idle...
One other thing, take the belt off and see if it still knocks? Or maybe the water pump knocking?

 

Make sure it is not in your drive clutch things do were out in there. My sportsmans have always had a knocking type of sound coming from the clutch. Check it out it might help just a thought though.

 

It's a 98', and I already thought about the belt and the clutch and removed them one by one and ran the machine and the noise was still there. The water pump on the other hand is an idea, the oil pump and water pump are driven off the same shaft that runs through the accessory gear