Author Topic: How to fix noisy Ducati Clutches, if you don't believe this is "character"  (Read 54583 times)

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Offline TopDOG

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Here's my old clutch noise for those who love it too


https://youtu.be/uj2oJ0MsOZU
Ducati is number 1, all others are number 2 or lower

Offline TopDOG

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Without the clutch noise it just doesn't sound Ducati I even have it as an mp3 on my phone to remind me what i will miss now until i die!! :'(
Ducati is number 1, all others are number 2 or lower

Old Rider

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Having now ridden the bike, I can report that the clutch is as smooth as before and the chatter while riding is all gone.
However, the cutch is more draggy than it was and gear changes feel more notchy.
Hopefully these problems will disappear as the clutch beds in again.
I can still find neutral, so all is basically fine  :)


Many thanks for the help

Old Rider

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Ok, on removing the plates I could see that the round hole referred to is the rounded bottom of each slot, so I did attempt to radius the tabs on the bottom plate to suit.
It was easy to file, so must be pretty soft steel...


On reassembling, I found the height of the stack was too great, so I tried again with just one friction plate at the bottom and this time all was fine and the clutch is now louder with the lever in than with it released.  Previously it was very much louder with the clutch lever released.
So, success!


Apart from being unable to fit two plates in, the main difficulty with this job is getting the plates out as you get towards the bottom of the stack.  I found this to be quite a game - or is there a trick of the trade??

Old Rider

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Brilliant.
I have been lucky enough to get a whole stack's worth of 1098 plates from a friendly local specialist (Peak Performance).
The grinding/filing mod appears to apply to the Paso end-plate - I can't see it being referred to as necessary for the doubled-up friction plates.  I hope that's right...


Gonna have a go right now - fingers crossed...

Offline VinceS

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So, all I need to do is find a dealer with a couple of s/h friction plates he's willing to part with, preferably steel and then place them in the basket/hub beneath the existing stack. Will any Ducati dry clutch plates do?
Yes, Yes, Yes and Yes.

The differences even up to 1098 are only in basket bearing & nut size and all the clutch plates interchange.
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Old Rider

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So, all I need to do is find a dealer with a couple of s/h friction plates he's willing to part with, preferably steel and then place them in the basket/hub beneath the existing stack. Will any Ducati dry clutch plates do?   The bike is a '93 999

Offline VinceS

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A friend with a 900ss has simply re ordered his plates by putting a friction plate in first instead of two plain plates.
Not possible! The correct answer is to put two friction plates in first. If just reordering them there will not be enough plate height left to make it to the top of the basket so the pressure plate would hit the inner hub and the clutch would never engage. The plain plates are the steel ones and they are what is already at the bottom of the stack so I can be very sure he didn't add one and make a difference! The idea is to put friction plates in first which go over the bottom of the inner hub and hit the bottom of the basket and lift what WAS the bottom plain/steel plate off the bottom of the inner hub. This is the action which causes the rattle to disappear (while the clutch is released).

This has silenced the racket beautifully
Assuming he has added steels further up the stack at best using one plate will be a short lived solution, I am surprised it works at all. All it can do is stop a bit of relative movement by setting up a kind of temporary clutch action between the bottom steel on the inner hub and the basket, this wouldn't last long before the friction plate lugs wear and the effect is lost. "Jumpy" starts would also be a high likelihood event for him!

but he says he's heard there's extra pressure put on the basket bearing by doing this. Does anyone know how true this is, if there have been failures
Yes there would be extra axial load but this is not a problem of consequence. Bearings have radial and axial ratings and this bearing already has a high radial component from the action of the gear drive to the basket. Adding the relatively tiny axial load from the clutch springs and expecting the bearing to fail is like farting and expecting the bike to wheelstand, it ain't gunna happen! It is already a widespread practice either by DIY as described here or professional solutions as mentioned below:
If you notice most aftermarket clutches have dealt with this issue in one way or another, they stack off the bottom of the basket and have typically got flat bottoms on their baskets so no "special" shaped friction pads are required. I have seen various slight variations on the way it is done but they are all an improvement on the original!

and how much of a problem it is to replace the bearing if it should fail?
If you regard "degree of difficulty" to change oil & filter as 1 out of 10, to do this clutch mod is about 2 out of 10 and to change the brg would be 3 out of 10, primary additional task being to undo the FB nut (B=Big) as shown in pic below (http://hunterdog.org.au/DiscussionBoard/index.php?action=dlattach;topic=193.0;attach=282;image)

I'd does sound a little too good to be true ...
Its true. Remember as discussed below NFI were doing this "quiet" mod before I pointed out they were only doing it half right and they stopped doing it rather than fix their procedure. Thousands of Ducati riders already have first hand experience of this working when done properly, so here's one more, or at least there will be when he does it properly!.....
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Old Rider

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A friend with a 900ss has simply re ordered his plates by putting a friction plate in first instead of two plain plates.  This has silenced the racket beautifully but he says he's heard there's extra pressure put on the basket bearing by doing this.
Does anyone know how true this is, if there have been failures and how much of a problem it is to replace the bearing if it should fail?

I'd does sound a little too good to be true ...

Offline VinceS

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just measured again with my verniers how far the friction plates protrude past the clutch hub bottom, exactly 2mm. ........  it appears to protrude higher than the 0.5mm allowance that is recommended

I just happened to look at this again and realise I never actually gave a direct answer to the question. That is because it doesn't really matter. But it is worth spelling out why. All that is actually required is SOME clearance - any clearance - between the first steel (which sits on the second friction plate in the bottom of the basket) and the clutch hub bottom (the top surface of the bottom flange). OK, so it is 2 mm for Chris's bike not 0.5mm as others have suggested - but that is fine. Presumably 0.5mm will disappear over time anyway as the reportedly dodgy filing beds in to the basket so 1.5mm will be left. Which is still fine.

Consider what would happen should the clearance go to 0mm. Again the load will be taken by the bottom flange of the clutch hub which means the rattle will return, maybe with the slight bonus that the extra 2 plates in the bottom will be rattling away themselves as there is now nothing to hold them still - unlikely to be audible! So the worst outcome of getting too little clearance is - back to original, not a problem and of course you will hear the rattle and know that filing job was even more crap than you thought it was, and presumably keep the now bedded in bottom plate and put a slightly thicker one above it. But would you do that from the start? ie put a very worn pair of plates in to ensure you only just clear the clutch hub? Not really.

Whilst you were asking about too much clearance I just want to point out the potential consequence of going the other way (ie too little) is more annoying than of too much, where what could happen is the clutch stack height simply ends up too high and you have to drop a friction plate and probably put a double steel in its place as taking out 1 friction plate would be too much and likely to bottom out the pressure plate.

That is why I was talking about stack height as the most important aspect of this set-up as the "unknown" here is how worn your plates are so the final decision is affected more by that than any other thing. The reality of exactly what you do at the bottom of the clutch pack will affect exactly how many friction surfaces you end up with before you hit the top limit - and that is also affected by how worn the plates are. So I don't really care about the supposed wear limits - if they have friction material on them they are good to go for a few more thousand km until you hit or are about to hit the bare metal. And you use different combos of steel thicknesses / qtys to make sure you always have a stack height that will not cause an actual problem, ie not too high that a steel could get wedged under the pressure plate, or too low that the pressure plate bottoms out. Nothing else matters, in the real world anyway! The worst thing that can happen if getting it wrong and running out of friction material is a slipping clutch and, unless one is a total mug and "smokes" the lot, this will be noticed and the bike can be ridden gently for 100's of km until a restack is conveniently possible.

As an eg of what is going on here try taking two (opposite) pressure plate springs off and just running with four springs. In almost every instance this will be just fine and clutch pull is reduced by 1/3. Remember the same clutch pack is used on 999's so it has considerable reserve capacity. Apart from a bearing change I think even the 1098's got the same deal, but don't quote me on that! I am just saying when it comes to clamping force and friction surface count there is a lot of scope to have one or two more or less and you will not see any effective change in the smooth and proper operation of the clutch. To me it is just a simple maintenance job and change the suckers before or just as you run out of meat! There is no reason it isn't the same for any average DIY'er as this is simple work and not much of a strain on the grey matter once you get out of the Ducati "guru" hocus pocus of it all and understand what is actually going on. It works just fine........

PS: The only very slight issue to using double friction plates in lieu of the now apparently unobtanium Paso end plate is that the double frictions are a tiny bit more flexible. This means they bend ever so slightly and in effect give better support near the outer periphery than the inner. This causes a very slight tendency for the rest of the clutch friction plates to wear slightly wedge shaped, ie the outer edge wears slightly more. Whilst you CAN observe the phenomenon after 10,000km or so, it is 9/10ths of naff all and the difference between a Paso end plate and double friction's might be 80,000km and 75,000km - which compared to the OEM set-up of 40,000km if you're lucky is rather irrelevant! But just felt I would add the info for any other equally AR types out there!
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Offline VinceS

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PS: Please do remember to replace the tiny little oil seal on the end of the clutch rod. They only last about 40,000km if you're lucky and then start to very slowly turn the dry clutch dust into black gunk as an oily goopy deposit gets on everything. These seals are about $9 each from CBC Mayfield (ph 4968 4000) and are 8mm ID x 12mm OD x 3mm thick standard lip G type seals. They are not a stocked item so its an overnight supply. Note if you try to buy them from Frasers the parts guys don't know that the clutch rod seals are not shown on the relevant clutch parts page, but on the gearbox layshaft that the clutch rod goes through - it is very confusing for parts guys that don't really understand what is going on in there!

I also always change the O rings on the clutch rod too, but have a box of metric O rings so just pick the right ones out of it without particularly remembering the size of them...... these at least are listed on the clutch parts page if you need to go OEM!
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Offline VinceS

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I wouldn't be too fussed about exactly what the clearances are at the bottom, what matters is that the clutch has the maximum range for wear without risking the top steel slipping over the top of the clutch inner hub and locking the clutch "open". This will be what the prescribed clearances are about achieving, so just look at it from that perspective and sensible decisions can be made.

Just to spell it out, you can easily see the stack height of the plates on the inner hub and then you either have observed or measured how much the outer spring carrier pressure plate moves when operating the clutch, and the total of these should leave the pressing face of the pressure plate overlapping the top of the inner hub, thus nothing can "get out", and wear will only increase the overlap. Going the other way there is a distance that the pressure plate bottoms out on the inner hub and this is the effective wear limit as when you get to it you lose clamping force immediately, as opposed to the slow loss of claming force due to the springs being more elongated as wear occurs. When you assemble the pack, before you have it fully stacked up you can put the pressure plate on and see how much clearance you have to this "bottom out" position, and make sure you are some distance above it. This logic is what all the numbers mean, and I would rather check from this perspective than anything else.

One small point is that on first installation of the double friction plate your filing of the landing angles will be "a bit crap" as everybody's is - all this means is there will be a tendency for a slightly higher "wear" rate at first which is really the bottom plate settling in. So you can go "a bit high" when deciding whether that final plate should go in. Remember the steels come in two thicknesses which from memory (dodgy!) are 1.5mm and 2mm, so a bit of fine tuning height is possible this way too. It doesn't matter so much that the filing is crap, what you are trying to avoid is the square to round phenomenon that doing no filing would get and will cause sudden jumping of the clutch, as all those dealer mods were doing before I pointed it out and NFI banned the practice in the country - rather than doing the job properly, bizarre huh!

If you notice most aftermarket clutches have dealt with this issue in one way or another, they stack off the bottom of the basket and have typically got flat bottoms on their baskets so no "special" shaped friction pads are required. I have seen various slight variations on the way it is done but they are all an improvement on the original!
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chris

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just measured again with my verniers how far the friction plates protrude past the clutch hub bottom, exactly 2mm.


Chris

chris

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Hello Vince, Thank you very much for your reply. Having read over your article again i realised you pointed out two plates could be used instead of the Paso plate, my mistake! However having now removed the clutch plates from the bike it seems just an unlucky coincidence that my clutch plates appear to be worn out, below the 2.8mm service limit, therefore new ones are on the way. In the mean time i decided to use your advice and round off the old friction plate fingers. Im struggling to get all angles the same as I'm using a file, as i dont quite understand how to make the template for the angle grinder?


Another thing is that by putting two friction plates in the bottom of the basket it appears to protrude higher than the 0.5mm allowance that is recommended (i got this info from the write up of this mod on the link you posted to the Ducati forum). I would say it protrudes by approximately 2.2mm above the clutch center bottom therefore one friction plate is not enough but two is too many. Do you think that by leaving out one of the two steel plates that go into the bottom of the stack first would be acceptable?


I apologise for all the questions but you seem to be very knowledgeable on this modification and i'd like to get it right first time round! 


Thank you once again, Chris

Offline VinceS

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G'day Chris, The alternate gets a mention in the text below - it is perfectly acceptable to use two friction plates in lieu of a Paso end plate. I did the M900 Monster this way and ~40,000km later it was as good as the day I originally did it. In that time the friction plates actually doing the work had mostly worn away so, since I was selling the bike and didn't want any local owner to be having any kind of issue with it, I put a fairly new set out of my ST4S when I put the slipper clutch in that. I also changed the basket as, despite that this mod stops the clutch rattle entirely, when you have the clutch pulled in and are stopped in gear you will hear the rattle if basket wear is excessive. What this mod does is totally eliminate rattle when stopped in neutral (which is the aesthetic benefit) and also whilst riding along in gear (which is the "greatly increased life" benefit). But any time you have the clutch pulled in you are stuck with the reality of whatever the actual clearances are so it is worth making those small and then you get the long trouble free life.

Annoyingly I have not figured out a way to shut up slipper clutches, either the Adler spline type (which despite my earlier posting does get noisier with time) or STM ramp type. With these they are quietest stopped in gear as in neutral they rattle away with all the "character" of a true Ducati clutch! But the safety benefits of hot corner entry risk saviour outweigh the noise / wear issues for slippers IMHO so it is a compromise I am stuck with for now.
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Chris

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Hi, i appreciate that this is an old topic but i'm planning on reducing the clutch noise on my Ducati Monster 900 sometime soon. The only problem i'm having is sourcing the parts, getting the two steel plates will be fairly straight forwards, as i'll just buy a new clutch plate set and reuse two old steel plates. However i cannot source a Paso end clutch plate, as what it mentioned in your article. Any idea where to get one or are there any other plates i could use to compensate?


I know its a long shot as this is fairly old but i thought i'd give it a go!


Thank you, Chris

Offline enzo906

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My (heavily Modified - read paid Gowie's property in Goulburn) Paso had the same clutch for 60000 as I would wash it all in Handy Andy and hot water every 2000K's (every oil change as the fairing would come off then) so it was squeaky clean. I never seemed to keep a bike alive long enough since :(
But I told a few other Dry clutch people and they do it too. So now I haved shared this with you.
PS at 60,000 my clutch still looked like new and I did burnouts and fannned it out of corners - generally abused the hell out of it, treated like my CR chook chaser's clutch.
I could generally take off without the shudder or noise etc from the lights too.
The late Multi never made it past 7000K's but then it was quiet so I never looked at it. The 12Multi was wet so again never tried it, the S4 died when it was 2,300Ks old but if it had survived I would have used Handy Andy on it too.

Offline VinceS

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I was just looking for something else and found this article again. I would add that, apart from the elimination of the rattle in neutral, the other thing that happens is you MASSIVELY extend the life of a dry clutch with this mod. The reason is that, with a standard set-up, every time you accelerate or back-off the clutch rattles to the other side of the free play between the basket / fingers / inner hub and impacts all the surfaces. So you are just riding along in gear and hammering the crap out of the clutch components. If you do the mod when you let the clutch out the plates actually stop all over the place, some at one end of the freeplay and others at the other, so basically there is no clearance and the push-pull thing doesn't happen on throttle changes and this eternal smashing of bits becomes history. They will still get a bump on gear changes, but this is mostly unladen compared to the banging of a full inertia back off / roll on that the standard set-up sees. As long as you are not a high rev take-off kinda rider you will see 100,000 km plus out of a standard clutch you did this mod with, otherwise it is a rare case that gets much past 35,00km off a standard set-up.

I also mentioned in the article the possibility of modifying the STM slipper clutch. This was going to be done by using the small springs that older style car ignition distributors use for centrifugal advance of the spark. However I didn't think these quite small springs could be securely fitted in a way that I was absolutely sure would never interfere with the proper operation of the clutch, so I abandoned the idea. The basket lasted about 25,000km before becoming too noisy however the plate to inner hub only had light wear so I have a new basket now and this will go into a race bike project "some day".

The REAL answer to a quiet dry slipper clutch turns out to be an Adler APTC (Slipper Clutch) for Ducati Dry Clutch, here is where I got mine http://www.store.commoto.com/product_info.php?products_id=97422. The only issue I have found is that every 5,000km or so they need to be dismantled and cleaned as the spline gets a bit sticky with the consequential effect that sometimes the clutch never re-engages after a gear change. It is quite startling when this first happens on the road, one soon figures out that a fast rev dislodges the stuck bits thanks to inertia and the maintenance can be put off to a convenient time. Otherwise in operation the clutch is brilliant, with a nice light pull on the clutch lever as a bonus.
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Offline VinceS

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Oh look, I have just discovered there is a write-up of this in Ducati.MS, using the less preferred but nevertheless OK two friction plate method, it is here http://www.ducati.ms/forums/showthread.php?p=276928

It seems people the world over have been fixing lots of Ducati clutches this way - and not dealing with and probably not realising that the square plates going in the round holes are going to be causing some of their presumed "operator error starts". The suggestion is made when using two plates to use the early model steel ones which are stiffer than the later model aluminium ones as installed in the ST4S per below.

But Brett's WD40 is a pretty neat solution too....
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Offline Brett

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G'day Vince,

That's a a good article and well done.

I actually use a much simpler response to queries on the noisy clutch.  I quickly explain that I use WD40 instead of engine oil, as it creates far less drag and less drag is, as everyone knows, more perfomance.  It usually ends a conversation I never wanted to have in the first place, right where it started.  Although it did create an awkward moment at my rego check on Saturday.

Not sure I'll be able to go back there, which is a shame...

Mvlti svnt vocati, pavci vero electi

Offline VinceS

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Edited to add a couple of extra bits, plus put a downloadable copy of this article at the bottom

Recently I got to do a lap of the Oxley, NSW’s best road!, where it was pretty obvious in mixed brand motorcycle company with a standard clutch ST4S along too that honestly these rattly clutches can be a bit of an embarrassment - and even more so to people who understand the engineering of what's going on. Of course, to many this racket is an integral and attractive part of owning a Ducati, I am not talking to you here, OK.....

For me having something flog itself to death just because enough attention to detail was not put in to the base design is pretty inexcusable. Fortunately, it can be fixed readily by those with only a moderate level of mechanical skill. You will also note that for the many aftermarket clutch kits available in different forms it is pretty normal to see that this issue has been addressed in amongst whatever the other features are provided. Unfortunately, not so with the otherwise brilliant STM Evoluzione 48T slipper clutch that I have fitted to my ST4S. However, because I have understood this issue well for a long time and it became topical again on the weekend I have now got an idea how to fix the noise from my slipper too, may put that up if it works. Check back here in a while and see if it turns up! (www.hunterdog.org.au/DiscussionBoard/index.php?topic=193).

Let me start out by saying that when I first bought a Ducati I asked if anything could be done about this noise and was told there was a standard fix to stick in a Paso plate and it only added $34 to the first service costs, so of course I just said to do it. I then found that the bike was quiet for sure, but increasingly I found it would sometimes stall on takeoff just after moving off, not operator error, and typically in the 2-3m zone - which of course sometimes puts you smack in the middle of the traffic!

I really wasn't getting straight answers about this so I pulled the clutch to pieces and did the engineering analysis thing on it. The really short story it was a poor solution basically due to lack of attention to detail and it was designed to cause this fault. Rather than changing the procedure to make it a safe modification as I expected, what Frasers did was black banned the practice to all dealers in Australia. So blame me if you have been told these clutches cannot be quietened down any more! But in fairness this is the only administratively practical response

However, I have now realised this all happened back in mid 2004 and I know how to fix it properly and cheaply, but it is probably a bit of a secret to most. But not any more - please remember that it might be easy to do right, but it was being done very wrong and Frasers didn't ban the practice without good reason, so proceed at your peril. This is your choices, not any advice from me that is happening here, what you do with the info is up to you, and that includes ANY consequences. OK, disclaimer now done those of you who have some mechanical nous and are well capable of thinking for yourselves you will not find this hard, and it is comfortably done in an hour start to finish.

Oh yeah, there is another bonus too apart from the considerably greater clutch life - clutch lever effort reduces about 10%. I once worked out why this happens, it is OK - but can't remember what the reason was now to tell you! I do remember figuring out that it is sensible to adjust the clutch lever closer to the bar so it only just disengages, as this itself also changes the clutch lever effort – when you study the bits you can see that the mechanical advantage changes as the lever comes in, it is like a mini-power booster effect and is available to anyone to use purely by adjusting the lever a little closer to the bar. But please remember, if you are having ANY difficulty selecting neutral when stationary you have not got this set right, and it will change a bit too due to temperature of the day / how you operate the clutch etc so you need to keep a little clearance in reserve.

I am not going to write up a full technical description of the clutch de-rattle procedure, just what I think of for now. Please also note that this will only keep the clutch quiet when the clutch is out (ie neutral / riding along) but when the clutch is pulled in most of the noise returns, particularly if the clutch was already fairly worn. But that’s OK as sitting at the lights in neutral and not rattling is a better practice than sitting there in gear and waking the tin tops from their slumber as they wait to see which part of your motorcycle falls off – as they expect it surely must explode soon and want to see it, but just not going through their duco!

What you need to do to start is to buy two standard steel clutch plates (used ones are just fine, as long as they are flat to 0.2mm) and a Paso end clutch plate. This is a steel clutch plate about 3mm thick (ie about double a standard one) and has friction material on one side. Maybe somebody will kindly find out and post the part number at the website above. Anyway, I would also note that, when I did this conversion to the M900 I was a slack tart and simply doubled up two standard old friction rings in lieu of the Paso plate and this has worked perfectly well for at least 10,000km now. I also had the Paso plate mod on the standard ST4S clutch for about 50,000km before swapping to the slipper, and that was to get the safety features of the slipper, not because there was any issue with the old clutch.

What happens with a standard clutch is the assembly of plates sits against a rim on the bottom of the inner hub. As you can see with the cover off it is easy to rattle the assembly through the clearance between the fingers of the friction plates and the slots in the basket, hence the noise - and the increasingly deep grooves / flattening of the mating parts. Ducati says the maximum slop here should be 0.6mm - but of course many let it get way beyond that. At least this mod will greatly slow the rate of further deterioration, but it won't eliminate it, after all these parts have to press pretty solidly on each other to generate our fun!

The clutch modification, whilst there are a couple of important details, is essentially as simple as taking the plates out, dropping the Paso plate in steel side first and then putting all the plates back and adding the steel ones to the top to make up the stack height so that the pressure plate doesn't bottom out on the hub. What happens is the Paso plate gets trapped in a fixed place relative to the basket and therefore in order for any of the rest of the plates to rattle they have to slip from wherever they happened to stop, and they won't be doing that as they are no longer bottoming out on the inside end of the hub! So the noise is totally eliminated, peace at last -now we can simply enjoy the exhaust note, ah bliss!

The really important detail that caused all the fracas in the first place is that the basket has milled round slots in it and the Paso plate has square ends. It’s the old square peg in a round hole scenario – it never worked the first time and trying it out on a bunch of whinging particularly ST owners didn’t make it any more successful!

What needs to happen is a bit of careful work on a grinder and finish with a file to very evenly make all the fingers on the Paso plate rounded so they fit snugly in the rounded basket slot. The simplest technique is to grind them all to an equal angle, say 70 degrees, and then grind half the angle off at say 55 degrees - and then round them all off with a file, which is what I did. But it would be best to make up a template with a 12mm (check) hole in a bit of 5mm plate to match the profile with a depth line scribed across it, probably this is the smartest choice! Do the same thing to all fingers at the same stage if you use the angled approach, rather than do them completely one by one which will only guarantee the last is not the same as the first. What you want is it sitting down evenly in the basket, you are not so fussy about the exact position it is in vertically, but don’t overdo it as you still want the top face of the fingers to be the original width.

You should notice that the top friction surface of the Paso plate when sitting nicely in the basket is just neatly proud of the adjacent end stop surface of the inner hub. It is this wonderful "coincidence" that allows the mod to work since the clutch plate pack is no longer able to land on the inner hub and therefore rattle. It is not impossible that end float / bearing wear / over enthusiastic grinding / filing may allow the Paso plate to go in a bit too far, in which case you would just need to throw in another friction plate. You need to check this to save the potential problem of a permanently rattling Paso plate and little / no change to the original noisy clutch problem - and spare yourself the inconvenience of dismantling it again to realise / rectify your howling blunder!

Please also note that it is really best to use the Paso plate rather than two friction plates, despite me saying I have done it on the Monster. This is because the Paso plate is stiffer and, while you may think it is pretty tough, even the Paso plate which is now supported at it's extremities will bend inward a little. This will have the effect of ever so slightly putting a radial taper on the friction pads, and this is in the opposite direction to that which the standard configuration tends to (slightly less) induce. It is not important, but it means a slightly increased wear rate will occur initially as the plates bed in to their new, slightly changed load profile. Probably this takes a 1,000km off the clutch plates’ life all together while it simultaneously increases the basket life by much more and greatly improves your sanity in the process. I would expect the use of double friction plates might bump this number up to 2,000km less life, but I don't think it is that important as when I pulled the ST4S's clutch out after 54,000km of mostly pillion duty I reckoned it had at least another 20,000km to go on the original plates.

The problem with NOT doing the finger rounding off I discovered is that quickly very small steps form in the bottom of the slot in the basket where the square edged Paso plate fingers hit the rounded basket slot bottoms. Mostly the Paso plate settles in these steps and everything is fine, but sometimes it stops while sitting out of the steps a bit, maybe only on one side. Then when you take off it starts engaging fine until suddenly it slips properly into the steps with a momentary release / grab action which is greatly accentuated at the lever and it is hard to avoid the pitch forward and stall routine.

What I did on discovering this issue was initially to simply grind the fingers at an angle, about 70 degrees, figuring it was a temporary fix while something better was sorted at dealer level. After more than 30,000km of flawless operation with this “temporary” fix I pulled it to bits to see how it was all going and could see that there were still steps forming in the basket, but further in and not able to support the Paso plate in a stable way out of it's natural resting place. But to remove any possibility of this problem occurring as things wore further or whatever I settled for rounding the fingers off properly then. The photos below show various stages of this process and if you can't work out what they are from the titles etc then you shouldn't tackle this job!

Obviously this process is going to reduce the stack height, ie the whole assy of plates would go further into the basket and the pressure plate would hit the inner hub before it made proper contact with the clutch plate pack. This is what the two driven (steel) plates are for, they go in immediately under the pressure plate, ie. at the top of the stack. Check the depth the clutch plates stack up inside the basket and how far the outer pressure plate goes before it hits the inner hub. With the extra steel plates you should have about 2-3mm travel spare to allow for wear of clutch material, but just check this carefully to make sure you are not near the end relative to your clutch plate wear / whatever. The workshop manual dimensions for the friction drive plates is 2.8mm minimum and clutch free spring length is 36.5mm minimum - it is worth checking these while you are there too.

So, Please now enjoy your nice quiet clutch - and the new found roar of your slip-ons!

Picture comments:

Clutch Plates, ST4S – 2003, Paso plate is on top of the pile. Note burrs removed from pressure plate

Clutch Basket ST4S – 2003

Paso Plate – Friction Side after initial modification. Note optical illusion, the angles are the same!!!

Paso Plate – Steel Side after initial modification. Note optical illusion, the angles are the same!!! (and if they weren’t when the photo was taken they certainly were on assembly as I made a template up)

Paso Plate rounded off and ready to go in again

Driven hub - as you can see wear will still occur due to all the abrasive crap still getting in the gap! I have been wondering if a variation of plate assembly around half life would get a greater total life, please let me know if you experiment further with this.

Basket Condition, note dent in bottom of slot (top of pic) where original square end dug in compared to the scrubbing marks of the “temporary” angled version a little higher up.

Paso Plate After 30,000km on “temporary” mod, note slight burring has started
« Last Edit: 11 Sep 2007, 12:53 PM by VinceS »
Vince Sunter  ( I'm ready, how about you? ); Check out these Riding Tips: http://tinyurl.com/4x3fk43 ;   Pillioning Tips: http://tinyurl.com/3r5dbz4

 

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