Wet clutch slipping

[MonsterHPD]

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.

   

[stopintime]

Hello Swede 

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.

[MonsterHPD]

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?     

[stopintime]

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...

[MonsterHPD]

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

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?   

[stopintime]

If a light lever pull is important, an APTC will amaze you compared to the non APTC  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...

[Speeddog]

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.

[Speeddog]

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).

[Howie]

Regular wet clutch or APTC? 

[brad black]

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

[MonsterHPD]

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



   

[stopintime]

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

Maybe they get a kind of glazed?

[brad black]

What does "make the beast with two backsall" mean



   

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

[Howie]

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.

[brad black]

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.