Ducati Monster Forum

Hello.

This summer the clutch of my M800 started slipping, mostly in top gear above 6000 rpm.
With some 27000 km, maybe it´s time to renew the clutch, but taking it apart it looks like new. Especially if you´re used to what the dry cluch use to look like ...

The friction plates are 3.4 to 3.5 mm thick, the steel plates are 1.5 mm and look like new, the whole pack is 43 mm high.

Are these numbers normal, or are they out of spec, and since the friction plates look OK, is it just a matter of restoring pack height?

I´ve used the same oil as always, so I don´t think that is the problem.

   

Hello Swede  [evil]

It's not strange that an eleven year old clutch is slipping at 27,000km. Discs and/or springs....

My first two APTC clutches started slipping at 25,000km at +/- 6,000 revs - after changing from full synth oil to semisynth the third one lasted 40,000km. My fourth is a 750, non APTC, and has ~40,000km on it without slipping, but it also has two extra discs.

Hi, Norge.

No, it´s not strange looking at mileage and age, but I had expected someting to at least look worn.

I don´t know the difference between the APTC (Ducati slipper /"servo" clutch...?) and the normal clutch, so I don´t know if the clutch baskets are the same. If they are, do you know ho high your clutch pack is with the 2 extra discs?     

No, sorry, don't know about heights.

What I do know is that only my first clutch showed signs of wear (blue steel discs) and that at least one, if not all, was inside specified heights and looked ok. Maybe wet clutches don't show wear signs like the dry?

If you don't mind testing things, maybe put in new springs first (maybe with a washer or two to add preload) and see how that performs. I don't think it's enough, but there's nothing wrong trying...

Of course I´m going to try a few things, just buying a new clutch seems a bit too easy ....  [roll]

I have not schecked, but the steel discs seems to the same as for the dry clutch so I´ll experiment a bit with pack height and maybe washers.
Since the bike is nominally my wifes, I don´t want to put in stiffer springs. It lready has a new slave cylinder to make the clutch lighter ...

When you buy clutches, you buy Ducati or do you use some aftermarket ones?   

If a light lever pull is important, an APTC will amaze you compared to the non APTC  [thumbsup] They are sensitive and require fine-adjustment to find both full engagement and disengagement. Stock 26mm slave is easy, 28mm difficult and I wouldn't go larger on an APTC.

Up to now, only stock clutches and no need to switch to aftermarket, but I was recommended Adige and Surflex as better options. Maybe I'll try one of those just to see if they are easier to modulate...

APTC plate stack minimum height is 50mm.
Individual frictions 3.2mm minimum.
Springs minimum length 36.5mm (this may be a bogus number, my dodgy memory tells me I've found it nonsensical regarding springs I took out).

The APTC clutch plates are totally different from the regular wet clutch plates.

I've had a few customer 800 APTC clutches that would slip like that, and all plates were within spec on thickness.

I got a set of Barnett plates for one, and they dragged so bad that finding neutral at a stop was totally impossible.
I've still got them in a box.
I replaced them with OEM.

I've added shims under the spring caps (washers) for the above OEM plate set, and the 2 (or so) other slippy sets.
Worked great.
12mm ID x 18mm OD shim washers.
I did the first clutch with 2mm thick shims, but... I had very carefully measured how much more I could compress the springs without them coil-binding.
That was the third time I had the clutch cover off of that bike to fix the slipping, and I wanted to not ever have the issue again.

Superglue the shims to the washers to enable assembly.

-EDIT-

After all that, I reread the original post, and the above means make the beast with two backsall for an '03 M800, as you've got the regular wet clutch in it.

Regular wet clutch:

Plate stack minimum height is 41.3mm.
Individual frictions 3.5mm minimum.
Springs minimum length 36.5mm (this may be a bogus number, my dodgy memory tells me I've found it nonsensical regarding springs I took out).

Regular wet clutch or APTC? 

wet clutches don't wear out, they go off.  that's been my experience anyway.

Thanks all for the input.
The clutch is a regular one, no APTC

Seems maybe a new clutch pack is the solution, after all ...? Strange that they should go off when all dimensions seem to be in spec.
Anyway, I will check if it´s possible to fit an extra plate an if that makes a difference.

Speeddog, you got me with this sentence:
After all that, I reread the original post, and the above means make the beast with two backsall for an '03 M800, as you've got the regular wet clutch in it.

What does "make the beast with two backsall" mean ???



   

For those with the language filter on, the forum replaces 'knull/knulla' with that expression  [thumbsup]
http://en.wikipedia.org/wiki/Beast_with_two_backs (http://en.wikipedia.org/wiki/Beast_with_two_backs)

Maybe they get a kind of glazed?

if you have the censor function on it replaces f*uck with "make the beast with two backs"

I looked up part numbers on clutch springs.  Wet 750 and dry 900, at least in '01 are the same number.  600 '01 (which feels notably lighter) is a different number.  '03 800 a different number, Heavier?  Lighter?  Dunno.  My 750, just sold, 72K miles, mostly urban on original clutch.  My buddie's 750, well over 100K miles.  Maybe 750 springs are the cure if caught in time?  Discuss.

maybe they started fitting crap clutches about 2002.  we had quite a few 620 sports (like the 2 or 3 we sold) with slipping clutches at very low km.

I didn´t even know there was a censor function. Obviously, I have to get rid of that, don´t want to miss out on creative language  ;)

With some luck I will soon have a spring tester, intended for fork springs but maybe OK for some clutch spring testing to compare my 900 springs with my 800 springs.

The steel plates don´t look glazed, but I suppose I could glass blast them just in case, maybe fit an extra disc if there´s room, look up the springs and maybe shim them a little, throw it all together and see what happens.  Even if my reference for "expensive" has been modified rather thoroughly since I got into the Ducati world, I thoroughly dislike throwing out a clutch that looks perfectly OK like this one does.

     

I've used a scotch-brite wheel on a right angle grinder to rough up dry clutch steel discs.

Less clean up than blasting.

Right ... I´ll visit the Baumarkt at first opportunity  [thumbsup]

you'll need thinner steels to fit an extra plate in.  with my old style 750 i ran the 1.5mm steels from (probably) the stash of old sintered sp/sps style packs, and then added another friction plate.  not sure how much thicker it was now, but they're different design and more restrictive (slave in cover).  it was noticeably heavier, but didn't slip any more.  i later just replaced it with a new pack (the horror) and again it was fine.  the pack in there was what came with it when i bought the motor s/h with 80,000km or so on it.

1098 has thinner steels i believe.

Does that mean a 1098 clutch pack might / would fit in the M800 basket / hub?

1098 has an extra friction plate, and is maybe 2mm or so thicker than an old dry pack.

And it would fit otherwise?

If so, interesting. It sounds like a 1098 clutch in an 800 would last forever .....  ;)

well, it's a dry clutch material and style, so i'd be wary of it.

Ooopps ... forgot that little detail  :-[

Anyway, thanks all for all the input. I´ll check parts and consider what to do. Since the bike is perfectly rideable as it is, and since nothing seems to get damaged, some experimenting might be worthwhile.

Hi again, Norge.

I´ve been checking up the clutch and am now evaluating options .... you mentioned above that your regular model clutch has 2 extra discs in it (presumably one steel, one friction).
How did you fit that in? I don´t see too much room for a thicker clutch pack since the locating tangs on the pressure plate will have too little "stick-in" on the clutch hub, and I don´t see much room for machining ..... so I´m curious ???
   

Don't know, a mechanic did it. I guess it's possible that he meant washers under the springs, but my impression was and is clutch plates. I'll ask later and get back to you.

OK, thank you very much  [thumbsup]

Well, time for an update, might be of interest to someone...

Sinc I felt bad about throwing away a clutch that looked and measured perfectly OK,  I decided to see if it could be salvaged. I did the following:

• Took 2 thin steel discs out and replaced them with 2 thick ones, increasing clutch pack thicknes by 1 mm
• Glass-blasted all steel discs; I never got round to the Scotch-brite ....
• Lightly dressed the friction discs with very fine emery paper on a glass pane; on all discs it was obvious that the friction pads were not flat; they all started sanding on a rather narrow part; I lightly sanded the until the whole surface was ground
• I machined ome 2 mm washers to put beneath the heads of the allen screws for the clutch spring, increasing pre-load by 2 mm 

Today was the tradiitional May 1st ride of the Ducati Club, about 250 km in 5-ish°C temperatures. Tested on the motorway, the clutch did not slip as it did last year (6th gear, >6000 rpm). So far, so good .... I´ll report when (if ...) it starts slipping again.

Apart from that, re-valved (softer) Öhlins shock worked  great over rutted roads, and the newly fabricated exhaust did not crack up :-)

(http://i855.photobucket.com/albums/ab117/Monsterhpd/Monster%20Forum/P4240023_zpsymc9j79u.jpg) (http://s855.photobucket.com/user/Monsterhpd/media/Monster%20Forum/P4240023_zpsymc9j79u.jpg.html) 

Hello,
time for another update in case someone might still be interested ....).

The clutch held up all of last summer, incluing some trackdays and quite a bit of road riding.

It was not perfect, though, but instead of "slipping up" when torque got too high, it sometimes "slipped down" on powershifts, slipping down to full grip.

Took the clutch out a few weeks ago, it looked exactly the same as last year, so I made some new washers and now run 4 mm pre-load washer. That´s the max I´d o with the stock screws, with any thicker washers I´d use longer screws.

Today was the first ride of the season for me, from a pretty cold spring with even sleetyrain not too long ago we now have had a few days of summer-ish temperatures. The M800 Dark got some pimp over the winter, mostly left-over bits from other bikes (Öhlins forks, turned-down flywheel, semi-radial master cylinder), but also some new carbon fibre.

Dry weightt (with oil) now is something like 169 kg, I´m slightly suprised at the weight  of these Monsters. My 900, with everything taken off that could reasonably be taken off, was something like 179 - 180 kg dry but with oil. The M800, with pretty much the same efforts weight-wise, is about 10 kg´s lighter. I had not expected this to be the case.

Anyway, in the background, white anemones (or whatever they might be called in english), there´s a billion of them and to me, this is the best time of year.

(https://farm8.staticflickr.com/7718/26580812930_475ddeb9b7_z.jpg) (https://flic.kr/p/GuRBC7)P5060034 (https://flic.kr/p/GuRBC7) by torbjörn bergström (https://www.flickr.com/photos/125016045@N02/), on Flickr    

Nice bike [thumbsup].