Topic: A rebuilt CB350K4 is making a "Chirping" noise.

[34barab]

Nearing the end of the engine rebuild after a complete tear down, I put 2 liters of fresh oil in the bike and buttoned up the crankcase side covers.  With the engine back in frame I tried the electric starter, which worked well, but I noticed a chirping coming from the engine.  It keeps cadence with the engine cycles, usually at a particular point in the cycle.  I think it's coming from left side of the engine, down low, possibly the alternator. 

No gas yet, carbs are on, exhaust pipes are off.  I don't want to run it yet.  All thoughts, suggestions, comments, etc. are appreciated.  Thanks

[cb750f-2010656]

Did you lube everything up good before installation?  Try priming the oil system before initially firing it up.

[robvangulik]

The alternator runs oilfree so it's easy to take the cover off to see if there is unwanted contact anywhere...
BTW what type/year is a K4?

[MoMo]

This is while the bike is being cranked over but not running?  Very common for the starter clutch springs and pins to go bad on the old twins......Llarry

[34barab]

No plugs and no gas.  I was using the starter to oil-prime the engine when I first heard the chirp noise.  (Is this sufficient to oil-prime the engine or should I add oil to the top end?)  The chirp sounds like metal on metal or metal on rubber.  Replaced the starter clutch springs, caps, and rollers during the rebuild.  No contact marks on the inside of the alternator cover.  You get the same noise kicking it over, and the chirp seems to occur at a particular point of the four-stroke cycle; but it's hard to determine precisely which point.  (I don't have a pressure gauge).  One thought I had: Even though the chirp seems to be coming from the left side, is it possible that one of the two small Cam Chain Roller Pin Rubbers that help hold down the Cam Chain Roller Pin got cockeyed or fell into the crankcase, causing the Cam Chain Roller to rotate at an angle?

[34barab]

Sorry, robvangulik.  1972.

[Gordon]

This is a 2-cylinder, correct? 

[MoMo]

No plugs and no gas.  I was using the starter to oil-prime the engine when I first heard the chirp noise.  (Is this sufficient to oil-prime the engine or should I add oil to the top end?)  The chirp sounds like metal on metal or metal on rubber.  Replaced the starter clutch springs, caps, and rollers during the rebuild.  No contact marks on the inside of the alternator cover.  You get the same noise kicking it over, and the chirp seems to occur at a particular point of the four-stroke cycle; but it's hard to determine precisely which point.  (I don't have a pressure gauge).  One thought I had: Even though the chirp seems to be coming from the left side, is it possible that one of the two small Cam Chain Roller Pin Rubbers that help hold down the Cam Chain Roller Pin got cockeyed or fell into the crankcase, causing the Cam Chain Roller to rotate at an angle?

possibility.  did you replace the lower roller and guide.  Most everyone I've seen was toast....Larry

[bryanj]

Is the compression blowing out the gasket, a lot of pattern gaskets for that model are real #$%*e

[34barab]

Yes, two cylinder.  Replaced the entire cam chain tensioner assembly with NOS components, and all the gaskets with a kit from Common Motor Collective.  How can I check to see if the compression is blowing out the gasket?  (Head gasket or one between crankcase and cylinders?)

[innovativems]

Is the sound coming from the stator cover?   Could be the starter clutch making noise as it turns over


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[34barab]

Link below is short video of the issue.  the chirp could be coming from the points.  I did lube the points cam.

https://photos.app.goo.gl/4unxVuWPnJgaqgRj6

John

[02z06dave]

Ive heard a noise like that twice before. Once the oil seal behind the points plate had been put in slightly cocked and the cam was rubbing it weird. The other time, it was a rubber intake manifold and that chirping noise was air getting sucked into a little crack in the rubber

[Don R]

 They all sound to me like they're flying apart. Especially when there's no exhaust or combustion.

[MoMo]

They all sound to me like they're flying apart. Especially when there's no exhaust or combustion.

That is one fairly accurate observation Don,  the old twin is one noisy motor.  Hope you had a great Christmas...Larry

[tbpmusic]

The alternator runs oilfree ...................

That's not the case, there is oil in there, just take the round cover off while it's running (like to use a timing strobe), and you'll get a facial (so will your timing light - put saran wrap over it).

[robvangulik]

The alternator runs oilfree ...................

That's not the case, there is oil in there, just take the round cover off while it's running (like to use a timing strobe), and you'll get a facial (so will your timing light - put saran wrap over it).

That was my (wrong) assumption for it to be a 350four, before this thread was moved to "other bikes".....