got the damn noise recorded finally

[br4inl3ss]

hi.
so after 2 PM here sayign all my problem was my carb, over 10 reply on another website and a french scooter help facebook group ( all saying all my idle problem is the carb ), i warmed it up, took a 10 minute ride it it reach real operating temp, and then sent it.
couldnt go over 54 km/h ( with stock 50cc it was hitting 61 on long flat with no wind ).
when back home after 20-25 minute ( didnt go over 20 km/h because weird noice was back, and metallic sound reappeared too ), let it idle, went to get my phone and recorded it hoping that it would pick the noice now since its louder than last season.

in case you dont know the back story , the whole engine was rebuilt, but the cam and rocker arm.
back then the metallic nosie was from way too much compression with the NCY 50mm bbk ( stock head ).
no one told me it was needed, because apparently first gen didnt need it but they changed it. where i bought it, no word about that.
so i kept the completly trashed 50cc stock parts ( broken piston skirt , loose crank, and so on ) and ran it for 3 months praying it doesnt break.

this winter i completly rebuilt the engine, minus the camshaft, guides, and rocker arm. 

today weird nosie is back, with metallic noise on throttle, and wont go over  54 km/h.

here is the noise ( PS yes the valve is noisy.. that became noisy on the way back home ).
sndup.net/dc2c

i have the cam and rocker on the way, but i hope it didnt destroy anything.
now maybe people will stop saying the the carburetor....

[GrumpyUnk]

I hear two sets of noise.
one being what i think is the rocker arm valve clatter at a high rate
the second being a singular noise at about half or quarter the rate of the rocker noise.
given the expected rpm of an idling engine, the second lower rate(occurrence) noise seems even lower than
engine rpm.
If I could draw the first on one line it would be repetitive and quick
the second line would be repetitive and spaced much further apart, like about 7:1 mentally counting from memory.

to my thinking the second, lower rate and a bit deeper noise is not crankshaft speed, but is even slower, so could be something further along the drive train, such as within the CVT or the final drive gearbox.

maybe move the recording microphone closer to the head, then the side of the engine(variator?) then the CVT
then the clutch then the gearbox to see if it is a localized noise.

adjusting the valves would make it easier to pick out what I think is the noise of concern.
tom
i played the sound a half dozen times...

[br4inl3ss]

its really hard to hear it on the video from someone that didnt ehar it irl it seems.
none ot what you describe is the noise im talking about.


no noise comes from the cvt. made my old variator solid ( cannot open/close ) and no belt, and no change. i can hear it comming from the top end. it seems to come from the head not the cylinder.

duno how to describe it. it ried to isolate the noise with audacity but i cannot get it right.
it sound like a washing machine... like a diesel truck at idle... maybe a variator with too small roller ? duno how to describe it.
but it is in the audio clip i can hear it ( barely tho ). its NOT a CLAPPING noise or any high pitch metallic noise.
maybe in a video ? i can hear it also

[norinradd]

It sounds like a an exhaust leak from the Head. I have this sound on my 52mm glixal bbk upgrade. It's like blowing air out your mouth and letting your lips flap against each other.

[oldunclestevo]

Kinda sounds like valve chatter to me. Double check valve lash?