Question about noisy clutch on '75 CB750 SuperSport

neuxstone

Hey guys, Any Idea of why my clutch sounds like a "box of rocks" on my CB 750?
When pull the clutch in it virtually goes away. Confused

I still have it on the stand after a year long rehab and it's ready to go besides that noisy clutch which bothers me.
Is it something serious or do they get this way after awhile normally?
The bike is showing only 17xxx miles. Looks to be authentic...

Almost sounds like the dry clutch on my Ducati, but that's s'posed to sound that way.

Thanks in advance Collectively; you guys have gotten me thru every issue I've had.
Dave

zjeppe · Posted: Thu Jan 28, 2010 8:00 am Post subject:

Them old sohc 750 were a bit rattly(if they weren't, they were usualy broken Wink

)However, it is difficult to make an estimation from overhere Confused

A sync job from the carbs might cure the thing(it does on a CBX Idea

)On the other hand, primary drive is done with twin roller chains whom have the tendency to stretch, but at 17 thou Question

It can be easaly controled by removing the carterpan and measuring the distance from the edge to the chains. It shoud not exeed 40mm if I'm correct, check the manual Idea

Good luck and keep us posted. Jef.

neuxstone · Posted: Thu Jan 28, 2010 8:16 am Post subject:

[b] Thanks Jef,
Those were my thoughts also, so I did the sync with carb sticks, Put the timing Dead nut on, and replaced plugs, tuned in the idle circuit and it helped slightly, but anything below 1600 rpm and it starts to rattle in un-rhythmic way.
I am doubting the primary as the problem because when I disengage the clutch, the noise goes away.
I am tempted to open her up, but don't have the time for exploratory surgery right now.
Dave

Russell · Posted: Thu Jan 28, 2010 2:48 pm Post subject:

A comment based on experience but not on any mechanical knowledge.
Several of my bikes from that era and on into the late 80's had a lightish(???) rattle from the clutch side of the cases at idle and in all cases the noise went away when clutch lever pulled in. A highly skilled mechanic and dealer that had sold me other bikes
said it was simply a characteristic of the design.He said that with some work and cost it would be possible to quieten the rattle down but he was sure it would come back in time.
We never went further than that. The bikes never gave any clutch trouble in use.

The bikes involved were all four cylinder machines.

With the GS650E that gave me 110,000 plus km, much of it hauling a heavy sidecar,the clutch was never apart.It was notice-able with this one that after one professional
'tune-up' that included carbs and valve shim clearance adjustments the rattle from the clutch at idle was considerably diminished.

It was one of those noises that I learned to simply ignore.

fasterspider · Posted: Thu Jan 28, 2010 3:53 pm Post subject:

Honda still has not gotten the clutch basket right after 60 years in business.
The basket in my CBX has been rebuilt and I bought a new basket for my CB1100F engine, they still make noise. It is the nature of the beast.
The clutch basket in my 2001 CBR1100XX makes all kinds of noise until the engine warms up and even still makes a little noise when she is warm. 46,800 miles on the same clutch with my hand on the throttle, amazing if not loud.

neuxstone · Posted: Sun Feb 07, 2010 8:04 am Post subject:

By the way, I have found the short answer to the Clutch noise if anyone is interested...
The CB750 Super Sport Clutch was redesigned using a circlip to hold the inner drive basket to the shaft instead of the standard nut the K models employ. It floats on the shaft which makes it prone to noise....Just thought I'd pass that on as the definitive answer to this question. Thanks all for your help! Wink

Dave

TireSmoker · Posted: Wed Mar 10, 2010 12:04 pm Post subject:

I'd like to jump on this thread - I have 79 CB750, which was not making clutch noise but suddenly is as half way through this morning's ride. Neutral, clutch in, idle speed, it's rattling like mad, clutch out, not a sound. I could accept that they are just that way, except mine hasn't been that way (just bought it last fall, only put a few hundred miles on it before winter, just took it out again, and only a hundred miles so far this year). Since it's a sudden change, I'm wondering what else might cause this? It's alarmingly loud, and I'm quite sure I should stop riding it and start working on it....

Thanks!

Dave

Russell · Posted: Wed Mar 10, 2010 5:28 pm Post subject:

I'd be concerned too. Usually the sort of clutch basket noises associated with multi's go away when you pull the clutch in.

TireSmoker · Posted: Wed Mar 10, 2010 5:50 pm Post subject:

Yes, well, when the lever is in the clutch is out - so what I mean is that it makes noise when the clutch is engaged in neutral, and does not make noise when the clutch is disengaged in any gear.

Dave

pd · Posted: Wed Mar 10, 2010 8:00 pm Post subject:

Why talk about it ?

Just tear it apart and inspect it . That's the only way to know one thing or another .

Qingdao · Posted: Wed Mar 10, 2010 8:13 pm Post subject:

My CB550 makes the same noise... I just figure I will wait for the motor to stop working then I will fix it. Razz

fasterspider · Posted: Wed Mar 10, 2010 11:52 pm Post subject:

You guys should hear a bad 79 CBX clutch basket, it sounds like a bunch of rods knocking.

fasthonda · Posted: Thu Mar 11, 2010 6:45 pm Post subject: Honda clutch

Make sure setting at clutch housing on motor is correct then check cable setting then get used to it as all my honda cb 750 bikes have clutch noise except 1 and that is a racing motor with different clutch than stock. If your clutch was air cooled it would sound a lot li Cool

ke ducati rattle that they sell as an ITALIAN THING>and dont worry about it. good Luck Fast Honda

TireSmoker · Posted: Sat Mar 13, 2010 10:56 am Post subject:

pd · Posted: Sat Mar 13, 2010 3:11 pm Post subject:

Yup , You'd know something might be wrong if parts fell in your lap . LOL

That factory service manual will do you good .

Like Ray suggested , you should sign up over at cb750c.com . That site is dedicated to Hondas 1979 to 1983 DOHC Custom 750/900/1000 .