New Owner, just put on new clutch pack and still slipping

[LA Duc]

Hi,

Any help would be greatly appreciated. New to working on this bike.

Recently purchased a 907. Clutch was in bad shape so I purchased a Barnett Clutch pack. Installed over the weekend with meticulous attentiion to diagram/stack height etc.

When I buttoned it all up there was some serious slipping. Much better than before I put the new clutch pack in, but not really drive able.

What do I check next?

Again, any thoughts or ideas would be much appreciated.

-paul

[ducinthebay]

What stack height number are you using? Should be the same for all later Ducatis with a dry clutch, which I kinda remember to 48.5mm or something like that. I keep the old metal plates so I can mix and match to get the thickest stack possible that stays inside the basket. I am assuming that they indeed are dry, and you didn't get oil on them.

The clutch pressure plate has a triangle on it, and it should be aligned to the screw boss in the basket that has the hash mark on it. If you don't get the pressure plate to seat all the way down, the clutch will slip.

If some one put an extra ball in the pushrod, or too long of a pushrod, the system won't return enough to allow the pressure plate to put enough pressure on the stack. Pull off your slave cylinder and and pressure plate and run a coat hanger wire through the hole to see what is in the stack. Refer to the manual for proper assembly.

And lastly, if the adjusting screw on end of you lever has been screwed in too far, the piston won't be allowed to return to home and vent the system, and you will build up pressure after a few pulls, and the clutch will start to slip. That screw is not for adjusting the lever position. Back it off a few turns to make sure its not holding the piston in too far.

Are you trying to do the quiet clutch modification? If so, confirm that its not interfering.

Happy hunting.
Phil

[LA Duc]

Thanks for your response. I ran through the list and checked it out on the bike. Notes below

I am using a stack height of 39mm. This is about 2mm higher than the stack that came out--but this makes sense given that the friction pads were totally worn out on the old plates. I checked with the original shop manual and this stack height seems correct.

I am not doing the quite clutch mod.

Regarding the pressure plate--I thought this might be the culprit. So I have it lined up properly with the notched post and arrow etc., but it still doesn't seem to be sitting down all the way. The teeth on the pressure plate only seem to go about halfway down onto the hub. This seems strange b/c the stack height is correct, so I would think that the pressure plate would go further down on the hub. Anything to this I'm not seeing? The plates are all pushed in as far as they can go. . .

Lever seems fine.

Thanks again for all the help--still not working right, though I have now taken all the plates out again. Should I try a shorter stack height so that the pressure plate sits lower on the hub? Any other ideas?

Thanks,

Paul

[blazing928]

Hi, FWIW, I had my Barnetts slip , i removed & cleaned with brake cleaner,light sand to remove glazing and never had problem again.

[ducinthebay]

39mm, sounds right. I guess the number I was trying to remember is 38.5mm. I always put in as many plates as i can get into the basket and not come out of basket when the clutch is pulled in.

Did you start with 2 steel plates in the basket first?

Take a few plates out and confirm that the pressure plate has full travel.
-If it doesn't, take out the pushrod and see if that changes anything.
- use modeling clay, or even a piece of paper to put between the pressure plate and basket to see where there is interference.

[Derek]

The stack height should 38mm ± 2mm. I found this article on setting up Ducati dry clutches a few years ago. Here it is below, it might be helpful in sorting out your problem.

Ducati Clutch Tuning Voodoo
submitted by Larry Kelly

Clutch Tuning Voodoo

Clutch engagement problems are quite common, but solving them often requires a fair amount of trial-and error work.
Usually, an uneven take-up or excessive slipping signals the need for a clutch pack replacement, often just caused by normal wear loss of the friction material on the plates. The mileage between replacements has a very wide range, anywhere between 3,000 and 30,000 miles, depending upon the amount of city riding and the rider’s launch style. If the clutch type is a slipper, it’s normal for the friction material to wear-out sooner since it’s function is to allow the plates to slip past each other under high engine-braking loads during downshifts. Some friction materials do better than others regarding wear and engagement smoothness, just like brake pads.

Sometimes engagement problems begin after you’ve just replaced your worn-out stock clutch components, upgraded to an aftermarket clutch or changed to a slipper clutch.
The key to smooth engagement is controlling the frictional force developed between the smooth plates (that are driven by the engine clutch hub) and the plates that contain friction material (that drive the rear wheel through the clutch basket.)

The amount of force developed between these plates is controlled by the stiffness of the clutch springs, specifically by the amount of preload on these springs. When the clutch is fully engaged, the friction force developed between the plates needs to be greater than the engine’s applied torque to prevent slip. About 430 lbs is needed on a stock superbike.
When you pull-in the clutch lever, the hydraulic pressure applied to the slave cylinder overcomes the spring’s preload and progressively reduces the force pushing the plates together until they begin to slip. During this time the dished plate(s) in the stack act to provide a progressive reduction in the inter-plate force as the plates separate a few millimeters and you get full disengagement.

When you engage the clutch the opposite occurs. The reduced hydraulic pressure on the slave cylinder allows the push-rod to move the spring-loaded pressure plate toward the plate stack (a millimeter or so) until the plates begin to touch. Keep in mind that when you move the lever you are changing the POSITION of the pressure plate. You have only indirect control over the forces between plates.
The forces between plates is controlled during this transition (between disengaged and fully engaged) by a dished plate that is included in the stack to smooth this transition. This plate acts as a spring (pushes back with a force) when it gets flattened between adjacent plates by the movement of the pressure plate.
So, the force pushing the plates together first come from the smaller force produced by flattening the dished spring plate, and later, a much greater force produced by the preloaded clutch springs.

The higher the height of the clutch pack, the greater the clutch spring preload. So, as the clutch pack friction material wears-out, the pack height gets shorter, until the force between plates is insufficient and the clutch slips, at first under high torque conditions such as at launch, and later even when the lever is not pulled at speed. Time for a new clutch.
This is also the cause of the annoying phenomena of clutch “judder” such that when you release the lever, and while the spring plate is being compressed, the clutch springs can’t develop a sufficient force to prevent slipping so the plates slip, grab for an instant (causing vibration-induced slip,) grab, slip and so on, until the slipping stops as the engine torque is reduced when the bike acceleration eventually drops-off.

Here’s the Physics behind it. The friction force developed between two surfaces depends on whether the surfaces are sliding past each other or not. For a given amount of force pushing any two surfaces together, less frictional force will develop between sliding surfaces, than between surfaces that don’t. Once surfaces are together it takes more force to get them to slide than to keep them sliding. Once they begin to side, however, they’ll keep sliding unless you push them together harder.
It’s these alternating higher-lower friction forces that cause the vibration that you perceive as judder. Sometimes adding a second spring plate to the pack will help to damp-out certain vibrations, so Ducati specifies a different number of flat plates, dished plates, plate thickness and stacking sequence for different models. The common spec however is stack height. Ducati clutch packs are stacked to 38mm ± 2mm.

Here’s some examples:
Haynes Manual: 748, 916, 996
7 friction plates - one curved plate with two friction surfaces
Minimum friction plate thickness = 2.8mm
2.0mm plain plate #1 2.0mm plain plate #2 3.0mm friction plate #1 1.5mm dished plain plate (convex side facing toward you) 3.0mm friction plate #2 2.0mm plain plate #3 3.0mm friction plate #3 2.0mm plain plate #4 3.0mm friction plate #4 2.0mm plain plate #5 3.0mm friction plate #5 2.0mm plain plate #6 3.0mm friction plate #6 2.0mm plain plate #7 3.0mm friction plate #7 2.0mm plain plate #8 pressure plate (line up marks)
38.5mm plate stack height

Haynes Manual: 916SP, 916SPS, 996S, 996SPS
8 (thinner) friction plates - two curved plates with one friction surface each
Minimum friction plate thickness = 2.3mm
2.0mm plain plate #1 1.5mm dished plain plate #1 (convex side facing toward you) 2.5mm friction plate #1 1.5mm plain plate #1 2.5mm friction plate #2 2.0mm plain plate #2 2.5mm friction plate #3 2.0mm plain plate #3 2.5mm friction plate #4 2.0mm plain plate #4 2.5mm friction plate #5 2.0mm plain plate #5 2.5mm friction plate #6 2.0mm plain plate #6 2.5mm friction plate #7 1.5mm plain plate #2 2.5mm friction plate #8 1.5mm dished plain plate #2 (convex side facing away from you) pressure plate (line up marks)
38.0mm plate stack height

Ducati Service Manual: 998
6 friction plates - one curved plate with two friction surfaces
Minimum friction plate thickness = 2.8mm
2.0mm plain plate #1 1.5mm dished plain plate (convex side facing toward you) 2.5mm plain plate #1 1.5mm plain plate #1 3.0mm friction plate #1 2.0mm plain plate #2 3.0mm friction plate #2 2.0mm plain plate #3 3.0mm friction plate #3 2.0mm plain plate #4 3.0mm friction plate #4 2.0mm plain plate #5 3.0mm friction plate #5 2.0mm plain plate #6 3.0mm friction plate #6 1.5mm plain plate #2 2.5mm plain plate #2 1.5mm dished plain plate (convex side facing toward you) pressure plate (line up marks)
38.0 mm plate stack height

Stack Height
A too-high overall thickness of the plate stack will cause drag between plates when the clutch is disengaged making it difficult to select neutral when the bike is stopped.
The last 2mm steel plate can be interchanged with a 1.5mm curved plate facing away from you if you want to adjust the stack to get the 38mm stack thickness, or if you want a more progressive, soft clutch engagement. A commonly-used substitution that adds an additional spring plate to the stack.
Any of the steel 2mm plain plates can be exchanged with 1.5mm plain plates to reduce stack thickness or increase stack thickness as needed to achieve your desired overall height. You will see the need for this as friction plates wear, so keep your steel plates from pervious clutch replacements as spares to be used as height adjustments later. The 2mm and 1.5mm steel plates only need replacing if they’re scored or warped.

[higgy]

Never use brake clean ever never ever, use a squirt bottle of water Bake clean will ruin any friction material...period Soap and water is all you should ever use then dry the components thoroughly.
Stack height is the usual culprit then order would be second. Ducati has revised it at least a few times and a barnett should make no difference

So this post may be deemed sacrilege, and I may be labeled a heretic. After this post I wouldn’t even be surprised to see an old tomato or two fly my way at this year’s BBQ. However, in spite of all this, I have a confession:

I’m not a huge fan of the Ducati dry clutch. That’s right…I said it.

Now, before the mob is formed, pitch forks gathered, and torches lit…don’t misunderstand. I don’t totally hate it. I mean, I own a “loud clutches save lives” shirt, and I used to have dry clutch envy back in my Monster 620 days. I very much like the fact that no pressure plate dust gets in the motor oil, and that clutch maintenance is simple as no fluids are involved. I’m also guilty of supporting the purveyors of open clutch bling.

My main, no only, issue is with the noise…but not all of it.

As we all know, the Ducati dry clutch makes two distinct sounds. The first occurs when the clutch is pulled in, and sounds like a cross between a tambourine and two metal plates sliding against each other. This sound is glorious, and I love it.

The second occurs when the bike is in neutral with the clutch out…and makes a clack-a-clack-a-clack sound. This is the sound of the friction plate tabs trying to beat the clutch basket slots into submission with each engine pulse…and is the subject of my ire. I hate how it drowns out the sound of my melodious Remus full exhaust …and it’s made worse by my beautiful open clutch cover, and the ~14,000 miles on my clutch (still stock).

Until recently, my only option to remedy the situation was to upgrade my ’04 MTS1000 to a new MTS1100…Dave R’s preferred option for sure …but I would lose all the dry clutch benefits, not to mention a good chunk of change. Then I stumbled across a post on how to quiet a Ducati dry clutch on Multistrada.net. The mod is apparently fairly popular with Ducati ST riders. Now, I know that any moron can give advice on the interwebs (including me), but I figured what the hell…I’ll give it a try.

THE MOD

1) Source a couple used friction plates. The guys at Ducati Seattle were kind enough to give me two of them after changing someone’s worn out clutch.
2) Remove all of the clutch plates.
3) Begin building the clutch plates back up by placing 1 or 2 of the used friction plates in first…before inserting the two steel plates (which usually go in first). Push the plates(s) in so the tabs seat in the bottom of the basket grooves. The goal is to prevent the “teeth” on the steel plates from touching the bottom of the grooves in the hub. It doesn’t take much to accomplish this, and I only used 1 plate behind the steel plates.
4) Install the remaining plates as usual.
5) Install the pressure plate as usual. You don’t want the clutch pack to be too thick, which may happen depending on your clutch. It happened to me, so I just left out the last friction plate. Turns out I didn’t need the extra old plates…but I didn’t know that beforehand.

So…the result? A gloriously quiet clutch when in neutral with the clutch out. However, the beloved sound with the clutch pulled in still remains, as does all the other dry clutch benefits. Since the friction plate tabs no longer try to beat the clutch basket grooves into submission, I should also see increased clutch life from this mod. Time will tell.

So far I’ve only ridden it on a test ride last night, and to and from work today. Clutch operation feels completely normal. In the name of science I even tested for any signs of slippage by doing a power wheelie from a stop sign on my way home tonight. No slippage!

Now there may be a downside to this mod. The plates are kept from rattling back and forth by being compressed between the pressure plate and back of the clutch basket (via the friction plate behind the steel plates). The may be adding a lateral load to the bearing on which the clutch spins. That bearing may see the load from the hub anyway though…I’m not sure, and haven’t dug out my clutch diagram to investigate. Word is there are quite a few Ducati STs with this mod which have traveled many thousands of miles without an issue. I’m giving it a shot…hopefully I’m not reporting back in the near future with a related problem.

So that’s my story. I’m not suggesting anyone follow suit, as I’m just another internet hack. I just wanted to share my experience, and serve as a role model for those who hate the clack-a-clack-a-clack sound.

Sorry…no photos…I’m a slacker, but the mod is really easy.

Flame suit on!

[ducinthebay]

yeah, I'm one of those ST riders who jumped on the quiet clutch bandwagon 7 years ago, and haven't looked back since. Never heard of any problem from this. I have 15k on my current clutch, with the quiet clutch mod. Did it on my 98 ST2, and then my '02 ST4s. No issues yet.


Cheers, Phil

[Derek]

yeah, I'm one of those ST riders who jumped on the quiet clutch bandwagon 7 years ago, and haven't looked back since. Never heard of any problem from this. I have 15k on my current clutch, with the quiet clutch mod. Did it on my 98 ST2, and then my '02 ST4s. No issues yet.


Cheers, Phil

I converted my ST4s to quiet clutch at 6,000 miles. When I replaced the original plates at 38,000 miles the drum and basket were still completely un-notched. I sold the bike a few weeks ago with 48,500 miles on it, still on the original basket and drum. The quiet clutch mod is beneficial to the life of the clutch components and stops them being hammered to death. Needless to say I have also converted the 907ie and my son has done the same to his 916.

[higgy]

[nickta]

Morning All.

Is the clutch mod a matter of restacking the plates that are there so a friction plate is at the bottom, or is there a little more to it than that? It seems to be a popular mod for all Ducati's. Just thinking it might be worth the effort of doing the job while the bike is parked up and in bits, or at least having a look.

Cheers.

Nick.

[ducinthebay]

The quiet clutch mod uses a spare friction plate, usually bent up a bit, to offer a small amount of friction between the basket and the hub so that the whole stack is simply preloaded, instead of accelerating and decelerating with every pulse of the pistons. You need an extra friction plate (or two) and put them into the basket first. Then you install the rest of the stack same as you would otherwise. Works like a charm. Ca. Cycle works (as best I can tell) developed the idea and sold a separate pre-bent plate with their kits for a while. The online community discovered you don't need their special part, and just bent up a spare friction plate from our last clutch upgrade.

Does not work with the previous version of the clutch on the 750/906 Paso, Sport or Pantah. Works great on all dry clutch Ducatis from '91 on (as best I know).

Do a web search for Quiet Clutch Mod, Ducati, and you will find a lot of info. Ducati.MS will be the bulk of your info, or the ST2 owners site on Yahoo groups. (that was a great site 2000 - 2010, lots of participation and some really cool mods, Really fell off when they stopped making the ST)

Cheers, Phil

[nickta]

The quiet clutch mod uses a spare friction plate, usually bent up a bit, to offer a small amount of friction between the basket and the hub so that the whole stack is simply preloaded, instead of accelerating and decelerating with every pulse of the pistons. You need an extra friction plate (or two) and put them into the basket first. Then you install the rest of the stack same as you would otherwise. Works like a charm. Ca. Cycle works (as best I can tell) developed the idea and sold a separate pre-bent plate with their kits for a while. The online community discovered you don't need their special part, and just bent up a spare friction plate from our last clutch upgrade.


Cheers, Phil

I gather the bent up bit is if your were going to fold it in half, but only gave it a small tweek?

The clutch is working OK, just a little rattle when out. I don't plan on replacing it any time soon, but one thing I have learnt with the 907 is never say I wont be doing that soon...... If you add an extra friction plate into the basket, wont it add to the stack height (see above)?

Take it easy.

Cheers.

Nick.

[ducinthebay]

The spare friction plate is bent in two places on the edge of your work bench so you are basically making a warpy washer out of it, but its only 4-5mm high if you lay it flat on the bench after bending. It becomes a bit of spring. Since you install it before any of the metal plates, it fills up the empty space between the metal plates and the bottom of the basket and puts some friction on the back of the first steel plate that never had anything touching it before. It does not affect your stack height, or your clutch function.

Cheers, Phil

[907pasonut]

...a quiet dry clutch...and simple enough to achieve, definitely give this a go
I fitted the closed clutch cover back on the bike years ago, if it works I will fit the vented cover back.
no matter what anybody says, desmo and dry clutch should always be kept on the ducati design