Author Topic: Anybody ever heard of a SQUEEKY engine noise? (Read 4020 times)

736cc · « **on:** April 20, 2007, 07:01:27 PM »

Bike runs like a raped ape but its got this mysterious loud squeeky-whining noise that only occurs when I back-off the throttle, and only while in gear under engine braking. Its coming from the motor but I cannot trace it. What could cause this? I've owned several dozen CB750's and this is a first. Doesn't sound insignificant.

Sweep · « **Reply #1 on:** April 20, 2007, 07:14:29 PM »

I had it and couldn't figure out what it was. I only rode the bike a couple of times before I tore it down. My suspicion is the oil pump.

750goes · « **Reply #2 on:** April 20, 2007, 07:54:09 PM »

does it happen in every gear ??

does the noise get louder under harder braking?

does it sounds like something might be running dry ??

merc2dogs · « **Reply #3 on:** April 20, 2007, 08:06:46 PM »

May be totally unrelated, but when I first got my bike there was a squeeky grating noise sometimes on acceleration, but mostly when engine braking, found it to be a spacer in the rear hub that was too short, made one up stuck it in and no more noise.

You could coast, or launch hard without the noise, but sometimes when gently accelerating, and always when slowing with the engine you would hear it

Of course I never found it untill after spending a great deal of time on the engine and clutch.

Ken.

Quail "Owner of the comfortable k8" · « **Reply #4 on:** April 20, 2007, 08:13:47 PM »

I had an exhaust leak that made a sound like a squeak when engine braking. Found it when I had a pipe off. MAYBE???

Jerry Rxman Griffin aka MuthaF'er · « **Reply #5 on:** April 20, 2007, 11:17:10 PM »

Don't cams/cam towers squeek or squeal when they are, shall we say, compromised?

jonbuoy · « **Reply #6 on:** April 21, 2007, 03:23:48 AM »

Mine had a simillar sound - like a dry bearing before I tore it down I was expecting the worse, my cam towers and top end are fine - the only thing I have found so far is the Clutch outer bearing (directly behind the cover) feels gritty and has lots of side play - I'm hoping this is the cause.

Steve F · « **Reply #7 on:** April 21, 2007, 03:26:57 AM »

Maybe (just a really "out-there" guess) the intake rubbers have a vacuum leak $:-\$ When decellerating with the throttle fully closed is when the vacuum is at it's greatest, and may be enough to suck air, making a squeeking like noise. I don't know, just thinking it may be something other than mechanical.

merc2dogs · « **Reply #8 on:** April 21, 2007, 07:59:59 AM »

Agreed, with mine everyone I had listen to it thought it came from the engine
I ran along beside it while a friend rode, and and it definately dounded like it was coming from the engine, I tore into mine pretty heavily and never found a thing until I worked on the rear tire.

Ken.

736cc · « **Reply #9 on:** April 21, 2007, 02:30:07 PM »

What can someone tell me about cam tower squeeky sounds? I removed a couple valve caps, theres oil in there but its not flying around. Sounds like a printing press w/ excessive clattering up there but it runs so good and I put 75 miles on it yesterday, runs like a champ. I did valve clearance check last week and I'm doing a re-check soon. Its not the chainguard or sprocket cover (I removed them as a test); can't pinpoint it.
I don't think its the rear wheel. Only happens during deceleration in all gears; pull in clutch, it stops. Clutch?
High-pitched mechanical whining during engine braking only in an early sandcast motor.

merc2dogs · « **Reply #10 on:** April 21, 2007, 04:30:39 PM »

Definately tear into trhe clutch, and check the primary.

on the clutch look for worn places on any mating surface

may need adjustment or the tensioner is worn.

look into the factory manual for inspection and adjustment procedures.

also check output shaft.

Ken.

736cc · « **Reply #11 on:** April 21, 2007, 05:08:19 PM »

I think its the clutch; with engine OFF and coasting in gear w/ clutch pulled in, its making that awful noise while in all gear. Is this a catastrophic failure about to happen, or just an annoyance until I tear it down?

merc2dogs · « **Reply #12 on:** April 21, 2007, 06:18:38 PM »

On my bike, I wouldn't take the chance and I'd tear into it first chance I got.

changing a bearing and clutch is a lot easier then replacing things you don't have to.

Ken.

mcpuffett · « **Reply #13 on:** April 22, 2007, 03:19:27 AM »

Hi 736, when the camshaft is running dry of oil it happens real quick and starts like a chirpping noise then if your not quick enough to pull the clutch in it turns in to a squeal then seizure

, sounds more like clutch side on yours ? , hope you get it sorted , cheers mick.

mcpuffett · « **Reply #14 on:** April 23, 2007, 01:37:56 AM »

Hi 736, have you managed to investigate your noise? cheers mick

736cc · « **Reply #15 on:** April 23, 2007, 05:09:56 AM »

It sounds like a noisy clutch; Sunday I went for a 150 mile ride w/ my bros and I avoided the noise by not using engine braking, bike ran and sounded like a champ. Very enjoyable day, 1st nice weather since last fall. Blew-out tons of carbon from the HM300's. Now I'm parking it semi-long-term and not using it until clutch is pulled and inspected.
Time for the next CB750 project, my K2 frame-off restoration is 99% done, its looking extremely nice, will give it a shake-down ride this week.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #16 on:** April 23, 2007, 08:12:29 AM »

That bike looks great (as usual). What I'd like to know is your secret for making the engine covers, etc look like new without the "polished" look. You sure you're not posting pictures of a new bike?

736cc · « **Reply #17 on:** April 23, 2007, 08:30:50 AM »

I re-finish engine covers w/ aluminum ceramic coat. My restoration shop offers this extremely durable and beautiful product, and sells CB750 covers re-finished (individual pieces or complete sets) ready to bolt-on. Please email me fo more info and pricing. detail@optonline.net

736cc · « **Reply #18 on:** May 25, 2007, 06:10:53 PM »

The bike did 125 mph today. It runs like a raped ape. This EXTREMELY OBVIOUS REALLY ANNOYING squeeky/whining noise only occurs during engine braking in gear, clutch engaged BUT NOT WHILE IN 1ST GEAR. Is there an explanation for this? What would cause the noise NOT to occur while in 1st gear???

jsaab2748 · « **Reply #19 on:** May 27, 2007, 08:06:14 AM »

Maybe prop the bike on the centerstand, take out the plugs, put the bike in 5th gear and somehow "drive" the engine with the rear wheel? Then listen to where the noise is coming from? Not sure if it'd work, but a thought...

merc2dogs · « **Reply #20 on:** May 27, 2007, 08:44:16 AM »

Can't say for sure what it is, but I'd inspect everything I could, pull the side covers on the engine and look for anything out of the ordinary, pull the pan and climb under with a flashlight and dental mirror, look for any score marks, or metallic residue. anything that can be opened inspect.

looks like a nice bike, And I would definately rather tear into it to see whats wrong and find some stupid little harmless thing than to ride and find out it wasn't so stupid, little, or harmless.

ken

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Author Topic: Anybody ever heard of a SQUEEKY engine noise? (Read 4020 times)

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