CB350 Squeaking Valve? SOLVED

E

ejether

Active Member
Hey all,

I've been working on this CB350 for months and finally got it started up. It running pretty ok but started to squeak/quack. It took me a while to locate the noise but I'm 95% sure its coming from the #1 intake valve. See link to video:

https://www.flickr.com/photos/thisriverlife/15439389106/

You can hear the wheezy duck / chirping as the valve depresses and returns. I'm hoping someone out there has an idea besides a bent valve.


History:
I got this motor on CL as 'rebuilt' but it wouldn't turn all the way around and it wouldn't shift. I rebuilt it again, it now turns and shifts. The bores had been honed, and new rings had been fitted and the valve seats had been machined/lapped and tested. There was a mark on one piston from possible valve interference. I don't recall which valve or piston at this point. I did not disassemble the head during the rebuild as it appeared that part had been done by an actual machine shop, not the guy I got the motor from.

Current status:
Me kicking my self for not removing that valve to make sure it wasn't bent and wondering how much damage is happening.
I have verified that the head is oiling through the inspection port and I have removed the cam holders to verify that there has not been any scoring indicating oil starvation. I have tightened and loosed the valves and ensured that the eccentrics on the valve adjusters are in the proper orientation
 
Re: CB350 Squeaking Valve?

sounds more like gunk in the valve seat. what happened when its actually running and not just turning over? As well is the Spark plug seated well?
 
Re: CB350 Squeaking Valve?

TheCoffeeGuy said:
sounds more like gunk in the valve seat. what happened when its actually running and not just turning over? As well is the Spark plug seated well?
Click to expand...

It squeaks while it is running, audible over the massively loud exhaust on it.
Sparks plugs have been in and out on this and I'm sure they are seated well when they are in.
Though that is a good point I forgot to mention. The sounds is diminished/gone when the plug is not in place.
 
Re: CB350 Squeaking Valve?

Could the noise be compression going by the valve seat? Did you check the seats and was it sealing?
 
Re: CB350 Squeaking Valve?

alzcbz said:
Could the noise be compression going by the valve seat? Did you check the seats and was it sealing?
Click to expand...


I did not check that. They appeared to have been tested when the head had been rebuilt prior to me getting the engine as they were dyed and I didn't verify. Compression is good in both cylinders however.

It could be compression leaking out but its so consistent even when the engine doesn't make a full rotation. You can see in the video, before I crank it over multiple times, that its chirping just as it jumps forward, then settles back. Would it generate enough compression so chirp even with no stroke?
 
Re: CB350 Squeaking Valve?

Is the breather tube obstructed? or are the oil journals obstructed?
 
Re: CB350 Squeaking Valve?

TheCoffeeGuy said:
Is the breather tube obstructed? or are the oil journals obstructed?
Click to expand...

The oil breather was unblocked when it started squeaking, it is currently blocked as I was tracking down the noise.
As far as I can tell, oil journals are not blocked. The cam holder oil passage was not blocked and the inspection port on the left side squirts oil from it while the engine is running. Is there another check you'd suggest?
 
Re: CB350 Squeaking Valve?

that is strange if you pull the carb can you feel it spitin back?
it has nothing to do with the breather...
run a compression test, also you can get a bar in there to depress the rocker and valve
it must be done correctly and carefully but is pretty easy to do,this will allow you to pinpoint it if it is a tight guide deal
and be sure the piston is down
 
Re: CB350 Squeaking Valve?

xb33bsa said:
that is strange if you pull the carb can you feel it spitin back?
it has nothing to do with the breather...
run a compression test, also you can get a bar in there to depress the rocker and valve
it must be done correctly and carefully but is pretty easy to do,this will allow you to pinpoint it if it is a tight guide deal
and be sure the piston is down
Click to expand...

I can try those things when I get home this evening.
 
Re: CB350 Squeaking Valve?

just make sure the exhaust valve is closed and the piston is down from tdc
on many engines the valves would hit each other trying to open both at once
and you dont want to bend the valve on top of the piston
 
Re: CB350 Squeaking Valve?

Damn loud for a valve seal. I have played it many times now. Very hard to tell where sound originates from in a basically solid block of aluminium with a few tens of parts moving.

Does the sound occur when cranking by hand or with the kick?
 
Re: CB350 Squeaking Valve?

GOT IT!
This was the key:

xb33bsa said:
that is strange if you pull the carb can you feel it spitin back?
Click to expand...

The noise not happening when it the spark plug was in, and not happening when the crank was turned were important clues too

I depressed the valve manually and that didn't come up with anything but when I took the carb off and put my hand over the intake book it squealed louder than ever. Turn out, the intake book gasket was not on tight enough as the screw were just a hare long. When the intake valve depressed and it pulled air in, this turned the gasket material into a 'reed' like a saxophone!

Pulled the intake, a little grey goop and some slightly shorter screws ad the squeak is gone!

Thanks everyone who commented and helped get me back to basics... and here I was about to tear the damn thing apart again.
Ain't it always the way.

Thanks again!
EJ
 
Re: CB350 Squeaking Valve?

Who knew your motor could be used as a musical instrument.
Glad you got it figured out.
 
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