I recently rebuilt my engine and from what I can remember (it´s been a couple of years since last on the road)this noise never used to be there. The only things that are different from before are the crankshaft and new pistons. The crank was second hand and before I assembled the engine I checked the bearings and they seemed ok (possibly slightly worn bit servicable). Regarding the water pump I don´t think this is related. When this noise appeared I thought the same so I removed the flywheel cover complelely and ran the motor without water for a short time amd the noise was still there. I´ve also checked the other side of the engine by running the motor without the variator attached, as this can rattle. I agree, I think the bike (sorry Scoot) is great and all the info we can get, the better. Regards Ian.