Hi, I have an 06 revup with ~100k miles that’s making this knocking noise on idle. It sounds like a low, slow knock. Headphones might help to hear it. Just did an oil change with 5w-30 a few 100 miles ago. I don’t drive often or far distances and check the oil level every time before driving. I’m fairly certain it’s not rod knock because I still drive it and would definitely be worse by now if it was rod knock. Engine still pulls very smoothly. It's not transmission/clutch related as depressing the clutch in/out makes no difference. Someone suggested a loose pulley, another mentioned piston slap. Just wanted to get some more opinions out there.

 

Just listened with headphones 3 times. To me that sounds like a bottom end knock. To really know for sure, I recommend listening with an auto stethoscope around the engine (top-end and bottom). It's possible one of your accessories is making the sound (like the PS Pump), removing the belts entirely and running the engine would quickly determine if that's the case. Piston slap is a possibility, you would see wear marks or scoring on the cylinder walls if you have bad piston slap. To inspect, you need an endoscope (mini-camera) and go through the spark plug holes. You can pickup affordable cameras that plugin with most smart phones, they work with an app and give surprisingly good image quality for the money.

I hope I'm wrong! I also have a Revup.
Cheers!
-Icer

 

Thanks Icer! I'll try out removing the belt and seeing it the sound still exists. In the meantime, I'll also to to pick up a stethoscope and endoscope. Now to find the time...