Engine noise after top end rebuild
 

I just installed a new 300cc S3 "A" cylinder and "A" piston.
Assembly went smoothly.
When I run the bike, it starts up easy as it should and runs fine. However, I am hearing a low frequency knock or chatter. Not a ping sound but a low sound.
This was not present a few hours prior with the old cylinder. So I can safely rule out low end or rod bearings or exhaust o rings right?

My question is. Is this normal for this to make this noise? Does it have anything to do with using 2 stroke oil to lube parts on assembly? How about cleaning my PV assembly? Maybe it is not yet lubed enough?

Here is a link to a video of the sound.

Anyone have any experience with this?

https://vimeo.com/60549378

Power valve rattle. You may need to adjust some free play out as now the tolerances are slightly diffferent. Also, a fresh clean PV will tend to rattle a little more than one with some hours of spooge and carbon accumulated.

Exactly what I was going to suggest too. Once they get some carbon on them they 1) reduce in total clearance, and 2) don't sound as metallic

I removed my side case cover and adjusted out any slack in the PV actuator. There was none. It has remained correct from my last adjustment. I did however clean my PV flapper and removed all of the carbon during my top end rebuild. It was pretty bad from before I jetted my carb.

Any way I can confirm it is the PV making noise and not something I should be concerned with? I do not wish to do any damage. I have had this bike for a year now and only have 30 hours on it. The rest of the time has been spent fixing issues, adjusting and waiting on parts. The last thing I wish to do is break something and have a major fix on my hands missing out on more and more rides. :)

Thanks for all input! :)

This play isn't in the plate preload. Its the side to side tolerance of the flapper valve itself once the drums and bearings are installed. If there was no clearance everything would bind up quickly. If you want to confirm to yourself, pull the exhaust pipe back off and stick your finger in the exhaust port (lol) and wiggle it around flicking at the flapper (more lols). You'll notice a very metalic clack clack clack as it slaps around. Up to you to decide if there is excessive clearance in there, but remember that some play is part of the design.

AHHH!!! That makes the most sense of all!!!!
The sound I hear in the engine is similar to the should I heard while I was trying to get the flapper out of the hole. Same resonant frequency.

Is there a spec? Should be using a feeler gauge to set this? The way I did it was to tap the left and right PV drums and bearings into position until they were flush on the outside of the case. The washer and screws laid flush across case and bearings. I made sure they weren't binding on the flapper but I did not check to see if there was too much play.

I wouldn't be concerned honestly. You won't notice it anywhere but idle and it will dull as you get some spooge and carbon on it.

I saw a thread where someone spaced it with a washer. I can't find it though.

I want to eliminate that sound for the sole purpose of being 100% sure that the sound I am hearing is not something else. Peace of mind.

Thanks for the info. I feel better about it now! :)

Pull the flapper valve out and run the bike without it. :D

A thin washer between the bearings on the LHS should reduce the clearance in theory. Be careful it doesn't bind up and cause more issues though.

Seriously, many have reported the clack of the powervalve (at idle) being much more noticable after a top end and clean up.