Topic: What is this clutch noise

[anteak]

Hola.
Situation:
76 750K6, 15k mi. just purchased, seems to have been fairly well maintained, runs and rides good after I replaced what appeared to be original tires. The clutch is the normal grabby, near the end of the lever travel engagement that everybody seems to know and love. All easily checkable maintenance items (drive sprockets, cables, neck bearings, swingarm bushings, brakes) appear to be good.

As I come to a stop, accelerate from a near-stop (but never a full stop) or coast at low speed while shifting with clutch disengaged, or partially disengaged/engaging/disengaging, there is a noise that sounds like a chain slipping over a totally worn out sprocket. At least that's how it sounded to me initially. A rattling, no crunching.
Then I noticed, during one of those times when the clutch was partially engaged, that I could feel a pulsing in the clutch lever when it makes that noise.

This is friggin' creepy. It's embarrassing as well. I'm worried that it's either going to spontaneously seize and/or blast itself apart in the middle of a turn while I'm decelerating. Bad form, either way.

Any insight? I have tools, a genuine Honda manual, no experience on Honda 4s. Nursed a $250 '78 KZ1000A2A  craigslist special back to life, but never ran into anything like this.   

Thanks in advance for your experienced insights.

[anteak]

bump for edit mods

[72500john]

 not a 750 clutch expert,  but almost sounds like your steel plates in your clutch are warped. is it less noisy/ grabby  when the engine is cold? hoepfully someone else will respond with more or better info. try the google custom search in the upper left hand corner of the screen and search for something like "cb750 clutch rattle". there are fixes for this..to a point.
hope this gets you started.

[BrockSamson]

On my phone so I can't double check my info, but will do my best from memory and what hondaman has passed on:

The 76-78 bikes received a revised clutch basket assembly.  Most notable is that it received a double plate to replace one of the single metal plates.  This was done to eliminate clutch "chatter".  So clutch noise threads about pre-76 bikes might speak to this.

I have experienced a noisy poor functioning clutch for a few reasons.  (Poor adjustment or adjustment came loose at case, cracked pressure plate, not enough oil on or getting to the friction plates and I was at one point flat out missing a part after reinstallation.)

If you have an impact screw driver (sears has an absolutely great craftsman impact screw driver for < $20) just put the bike on the side kickstand, pop off the clutch case, remove everything and get measurements on your springs and friction disks.  You can also examine them to see if anything is warped or damaged.

In another thread called "clutch advice needed" that I started I have a link in the very first post that will take you to the procedure for pulling out the clutch basket.

If you do pull everything out be sure to read through that thread at all the mistakes I made and the advice of mcrider, hondaman and a few others.  My bike is a 77 but everything should apply to your 76. 

Sent from my HTC Sensation 4G using Tapatalk 2

[anteak]

Based on what you all have offered, and my searches have turned up on the forums, I'm going to order a CycleX full kit so that I get the steels as well.

After all, I was pretty beat up at 36 years old, despite my relatively low miles 

And I'll be back on here again when I screw up and miss some crucial installation step, I'm sure, whining for advice and a reality check.

Gracias to all.

[NewOldSchool]

The clutch is probably out of adjustment.

Mine did the EXACT SAME thing, if it is too lose the clutch release mechanism will skip skip skip when lightly applied. (aka when slipping the clutch)

Do as the manual says and properly adjust the clutch, if this does not solve it than order a clutch kit.

Also re-check that your drive chain is taught, this will enhance the jerky feeling if it is a bit lose.

[BrockSamson]

Here is the thread I spoke to earlier:

http://forums.sohc4.net/index.php?topic=109380.0

[trueblue]

I'm not sure if the 750 has the little bearing on the clutch lifter like the 650, if this is going bad it could give similar symtoms.

[BrockSamson]

It does:

[Brantley]

I'm with trueblue. If that 6003 bearing is noisy when you spin the lifter plate in your hands the sound is super amplified assembled and running.

[immortal]

anteak, I have exactly the same issue with my clutch, a 1976 CB750F1 and my clutch is brand new OEM Honda my second one in less than 500 miles. I did have the Ape clutch that was brand new also and I had the same thing and thought it was the Ape set up. My issue is the exact same description, sounds like a sloppy chain, weird noise and noticed it worse when pulling away cornering.  Sounded horrific today after a decent long ride through town.

I think I have it tracked down to a warped "clutch Pressure plate, for me part # 22350-300-030, as it is the only thing that is not new and I'm 100% sure I have the correct clutch adjustment. I'm going to replace the plate but let us know if you resolved it and I will do the same as soon as I locate a Pressure plate.

[anteak]

anteak, I have exactly the same issue with my clutch, a 1976 CB750F1 and my clutch is brand new OEM Honda my second one in less than 500 miles. I did have the Ape clutch that was brand new also and I had the same thing and thought it was the Ape set up. My issue is the exact same description, sounds like a sloppy chain, weird noise and noticed it worse when pulling away cornering.  Sounded horrific today after a decent long ride through town.

I think I have it tracked down to a warped "clutch Pressure plate, for me part # 22350-300-030, as it is the only thing that is not new and I'm 100% sure I have the correct clutch adjustment. I'm going to replace the plate but let us know if you resolved it and I will do the same as soon as I locate a Pressure plate.

I still haven't installed my clutch setup yet. Wound up with the APE set, complete, steels, frictions, may even have gone for the pressure plate too, I haven't opened the box yet.

Have you had any luck with YOUR pressure plate fix? I got side tracked by a front end that was scaring me a bit....and it had a bad seal leak. Wound up needing a new leg so I replaced the set and new seals and what I thought was bad bearings turned out to be bearings that were undertightened and the lube was pretty dry. I chased down all the balls under the benches, compressor, freezer, garage fridge, other bikes, tool chest, lotsa fun, but I found them all and mic'd 'em and they were all even sized and nicely round, and the races were like new. But I was already there so I swapped for a set of AllBalls. I'm typing this while on a break from wrestling the legs back into the trees. Like I always say, any damn fool can tear a bike apart...it takes a SPECIAL fool to put one back together 

So, anyway, I'm gonna get back to it now. I got a commitment from my paint guy. He got a real job and went out of the paint biz but promised he'd do my two Hondas, so I'm super stoked.  He's had bikes featured in Cycle World and won a Second at the Bonhams invitational in Monterey or Carmel or wherever it's held, so my babies will were pretty clothes.

L8r,
Barry

[immortal]

anteak, Thanks for the reply!

I did replace the clutch pressure plate and....it makes no difference, its very weird and frustrating.  So when I started out with this clutch chatter issue like an idiot I kept adjusting the chain, by the way my chain and sprockets are new 530 Xring. After wasting my time with the chain adjustments, I figured it was definately coming from the clutch so I changed out my clutch for a good, "well within specs used set", no difference at all so I threw down the money on the Ape set, again no difference and totally frustrated because this is the final fix for the entire build.  Frustrated I purchased a brand new OEM set complete with discs and plates.....no difference. 2 clutch plates, 2 baskets and new cable etc. I have even replaced the whole clutch cover assembly.

Its exactly as you described its right in the sweet spot of clutch release. As you know there is a very short window of release with these clutches and within that, the clutch feels like its grabging causing the chain to chatter within the release. If I'm in very slow traffic I have to fully release the clutch as I'm creeping forward so its clutch in or clutch out you cannot ride that clutch hardly at all without hearing that chattering sound.
In honesty I'm not noticing it quite as bad as it was on the turns but it is still there perhaps I am subconciously releasing different or more quickly to reduce it but I was at one point noticing it very bad on slow tight turns especially on an uphill grade.

In fact I have to take my CA motorcycle test in the next couple of weeks and its going to be really tricky doing the slow tight test circles while this clutch chattering away and distracting me.

It would be nice if one of the old timers could respond to this as I'm sure they must have some idea. 

Please let us know how it goes and "if" I get this resolved I will post it here.

Cheers!

[iron_worker]

Does this happen at a specific RPM? Are you just luggin the bike down too much and it's chattering?

IW

[immortal]

I wouldn't say it happens at a specific RPM although I will make note on my next ride. Its just on the flat or a grade, just one up, no extra weight.. worse under any kind of grade even a lightly graded driveway up into your garage to literally coasting in 1st or second in very slow creeping in traffic you can hear it/feel it...even pedestrians look around wondering what that sound is if you don't engage instantly.

[immortal]

Can any of you old timers offer any advise on this clutch grabbing?  I'm stuck at a bike that is 99%.....any insight greatly appreciated!

[KRMK3]

Are you sure it isn't worn out primary chains and tensioner and maybe also the primary cush drive ? Can't see it being the clutch (or rear chain) as you have already covered that base. If the primary chains are worn out and slack they could well make the sound you have when you start to release the clutch and the drive is taken up. Out of synch carbs may accentuate the problem.

[immortal]

Thanks for the reply...greatly appreciated!

The Primary chains are New from Ape plus I purchased a new NOS tensioner.  Seems like I went through almost everything, however...The cush drive...thats new to me!....Do you mean the rear wheel drive cush wheel rubbers that go in the rear hub? I do seem to remember one of them being a little rough during reassembly.  It would be nice if it was that as it will be an easier replacement.   Although I fear you are talking or another part?

Carbs are dialed in pretty tight and bike runs great, she does not like to idle below about 1250rpm thats about as low as I can get it with my gauges.

[KRMK3]

 Item no. 4 (sprocket driven) in this CMS link :-

http://www.cmsnl.com/honda-cb750k6-four-usa_model14380/partslist/E16.html#results

This sprocket unit contains some shock absorbing rubbers to cushion the drive on take up. They age over time and wear with high mileage. I believe someone (or maybe a club) in Germany had some of these rubber blocks made a while back. I guess you just grind the rivets off the face plate, remove and replace the old blocks with new ones and re-rivet it back together with new rivets. I believe Honda supplied the sprocket assembly as a complete unit only.
  I am not sure that this alone will cause your problem though !   

[Old Scrambler]

I've been running the same clutch in my K3 for over 70,000 miles. Last year it started to chatter and make a low-pitched squeel when under load.  I followed the instructions in the manual to do a proper adjustment and all is good.

If your bike was not overly abused, the clutch parts should last a long, long time. The biggest amount of typical abuse is dirty oil, followed by low or no oil, followed by a combination of hand-slipping in heavy traffic and having the wrong oil for that type of traffic condition.

A common error when assembling the clutch is reversing the direction of the 'swirl' on one or more of the fiber plates. This will trap oil and cause slippage, chugging, and wierd sounds. Another mistake is bending or breaking a tap on the pressure-plate, or over-torquing the cap-bolts and slightly stretching the threads which allows extra play in the clutch. I have replaced clutches on several CB750s and have always had good success. The clutch-pack itself is seldom the problem. BTW....clutch parts from the F2-3 models are different from the CBs.

I switched oils two years ago and now use SHELL Rotella. It changed how my clutch felt and contributed to the need for adjustment, but after the adjustment all is well and smooth as can be.  When you adjust the clutch lifter, be sure you are not backing-off too much. When you adjust the hand-lever, be sure it has free-play when released.  On a new clutch, you may need to re-adjust at the clutch and then at the hand after the first few miles.

Regarding your idle........get it fixed. You don't need a synch-stick to get all 4 carbs in synch to idle smoothly at 900 rpms when the motor is hot.  If you have 1 & 4 or 2 & 3 out of synch, this will cause additional chatter on the chains and clutch.  That condition may also be the result of faulty timing......on just one pair.....this may be caused by a dirty advancer that does not allow full retard.....quite common for bikes that 'sat' for a few years. 

[immortal]

I've been running the same clutch in my K3 for over 70,000 miles. Last year it started to chatter and make a low-pitched squeel when under load.  I followed the instructions in the manual to do a proper adjustment and all is good.

If your bike was not overly abused, the clutch parts should last a long, long time. The biggest amount of typical abuse is dirty oil, followed by low or no oil, followed by a combination of hand-slipping in heavy traffic and having the wrong oil for that type of traffic condition.

A common error when assembling the clutch is reversing the direction of the 'swirl' on one or more of the fiber plates. This will trap oil and cause slippage, chugging, and wierd sounds. Another mistake is bending or breaking a tap on the pressure-plate, or over-torquing the cap-bolts and slightly stretching the threads which allows extra play in the clutch. I have replaced clutches on several CB750s and have always had good success. The clutch-pack itself is seldom the problem. BTW....clutch parts from the F2-3 models are different from the CBs.

I switched oils two years ago and now use SHELL Rotella. It changed how my clutch felt and contributed to the need for adjustment, but after the adjustment all is well and smooth as can be.  When you adjust the clutch lifter, be sure you are not backing-off too much. When you adjust the hand-lever, be sure it has free-play when released.  On a new clutch, you may need to re-adjust at the clutch and then at the hand after the first few miles.

Regarding your idle........get it fixed. You don't need a synch-stick to get all 4 carbs in synch to idle smoothly at 900 rpms when the motor is hot.  If you have 1 & 4 or 2 & 3 out of synch, this will cause additional chatter on the chains and clutch.  That condition may also be the result of faulty timing......on just one pair.....this may be caused by a dirty advancer that does not allow full retard.....quite common for bikes that 'sat' for a few years. 

Hey Thank you taking the time to reply.  You make some good points with good advise. Since the rebuild I only have about 1400 miles. The clutch and plates I have around 400 miles.  I was using the Rotella then switched to Castrol 20/50. My oil is good as I just completed my 3rd oil and filter change 50 miles ago I figured I would over do it on the oil changes for these first 2000 miles and as I see the oil getting darker I was changing it to get any crap out I may have missed.

The bike runs very strong and I keep checking and cross checking my carbs but I think you are right. I need to find somone here In Southern California who is really talented at working on these bikes but unfortunately there seems to be no one in Orange County I have been able to find.  I did take my bike to Jay Larossa...moving on I need to find somone who is interested.  The ignition is also new its an electronic ignition and tests show it to be spot on.
Carbs and fuel lines etc all have been rebuilt and gone though. My feeling is somthing is ever so slightly off but I dont quite have the skills necessary.

Perhaps I should a little more closely at the clutch adjustment "again" lost count how many times I have dome that, im following the book to the letter but perhaps I should try again and clsely monitor how much im backing off.

Many Thanks for the advise!

[Hoffsquig]

Sorry for resurrecting this old topic, but this is the first one I've seen that matched what I'm dealing with.  My CB750 (K6 engine/clutch basket) has this exact problem and I hoped the original poster found a solution?  The bike operates perfectly, except for this issue.  It typically gets worse as it warms up.  When coming to a stop or accelerating from a stop, with the clutch lever right in the "sweet spot" between engaged and disengaged, it "pulses", "chatters", "slaps"....it's hard to describe.  I can feel it throughout the bike, generating from somewhere between my feet.  Definitely sounds a lot like a chain lightly slapping the case.  It makes taking off from a stop a little tricky, as you have to either have the clutch fully disengaged, or fully engaged to avoid the chatter.  It only happens when travelling slowly in the middle of the clutch range.  doesn't change with load (uphill/downhill/passenger)

I've inspected the clutch basket and lifter plate, both look good to me.  I replaced the entire clutch pack with new friction discs, steels, and springs just in case.  Ensured the swirling on the outside friction disc is the right direction. Adjusted the lifter plate screw.  Adjusted the clutch cable per the manual, and tried adjusting in various ways not "per the manual".  Adjusted the chain tension per the manual.  Nothing gets rid of it.  (Side note:  while I had the clutch cover off, I noticed the kick start shaft has a little side-to-side play to it when it's not routed through the seal on the clutch cover...is that normal?)

All I can think of to do still is get it off the rear wheel and see if I can reproduce it in the garage, where I can feel around for a better general location of where it's coming from.  What all is visible if I drop the oil pan and look around?  Can you evaluate any of the transmission or primary chain from that point?  I'm really hoping I dont have to pull this engine again, I just finished this project after 3 years.

[david 750f]

If you drop the oil pan you can check the primary chain tensioner. I believe the specs are 65mm new with a limit of 70mm. The manual shows how to take the measurements.

[PeWe]

My K6 had a rattling sound as the metal plates could rattle around a few years ago.  Like one disk/plate missing with too much play inside.

Happened at take off sliding on the clutch leaning bike a little to the left if I remember correctly. Maybe more when warm.

Maybe the clutch arm was a little too loose. The screw that must be tighten to stop, back out 1/4-1/2 turn and lock it.
My engine had tight primary chains, primary hub rubbers replaced.

I upgraded the entire clutch to an F2 clutch with double riveted metal plate. Reused the old fiber disks and metal plates too. Then really good with no rattle at all.

My K2 with its stock clutch has not such rattle.

[TwoTired]

Sorry for resurrecting this old topic, but this is the first one I've seen that matched what I'm dealing with.  My CB750 (K6 engine/clutch basket) has this exact problem and I hoped the original poster found a solution? 

Since it is a wet clutch, oil matters.  What type, weight, and brand are you using?

Cheers,