Clutch Piston

Desmo_Demon · Post by **Desmo_Demon** » Thu Apr 05, 2007 12:20 pm

PascoPaso wrote:I know I am a late comer to this, but can you offer some suggestions and somewhere to purchase the parts on the West Coast, USA?

http://www.proitalia.com may have one on the shelf. If not, you can always pull the bearing out and either find the part number on it or take measurements and buy a bearing through any place that carries bearings. If you have the dimensions, you can go to http://www.skfusa.com and eventually find the part number of the bearing you need.

Post by **jcslocum** » Thu Apr 05, 2007 12:21 pm

Have you looked thru the Tech FAQ at the top of the page? It has ton's of detail for the clutch.

The bearing is avalable and the seal can be upgraded to a better design. It's the little button that is no longer made.

Post by **paso750** » Thu Apr 05, 2007 7:52 pm

Hello guys,

http://forums.ducatipaso.org/viewtopic. ... ch+bearing

bearing 608-ZZ

I searched the web and found the dimensions:

8mm inner diameter
22mm outer diameter
7mm width

http://www.agrolager.de/product_info.ph ... d=11062008

It says that "ZZ" or "2Z" is the same (metal shielded on both sides, btw. "shielded" does not mean "sealed")

G.

PS: just added this info to the FAQ

Desmo_Demon · Post by **Desmo_Demon** » Thu Apr 05, 2007 8:00 pm

paso750 wrote:bearing 608-ZZ

I searched the web and found the dimensions:

8mm inner diameter
22mm outer diameter
7mm width

http://www.agrolager.de/product_info.ph ... d=11062008

It says that "ZZ" or "2Z" is the same (metal shielded on both sides, btw. "shielded" does not mean "sealed")

G.

Here is the SKF USA website showing the 608-2Z bearing that Paso750 states...

http://www.skf.com/skf/productcatalogue ... startnum=4

PascoPaso · Post by **PascoPaso** » Thu Apr 05, 2007 9:44 pm

I will order the parts and let you know what happens. I will pass on any information I can on the status of the button and it's composition?

Post by **paso750** » Fri Apr 06, 2007 9:16 am

btw. the pin dimenstions are:

______________
I.............................I
-------.........--------
..........I.......I
..........I.......I
..........\___/

diameter top: 16mm (0,63 inch)
total height: 9,10mm (0,358 inch)
height of flat top: 2,20mm (0,086 inch)
diameter of the lower section: 7,97mm (0,314 inch)

An M8 bolt has a 13mm head (e=14,38mm, see link below), so even if it not 100% matching the easiest way would be to shorten an M8 bolt (I`d suggest DIN920 as these have a thread only at the end) and machine down the head.
Interesting in this case would be how long the non threaded section is, but I guess at the end it doesn`t make any difference also if you use a finethreaded bolt with thread up to the head (DIN961).

http://www.online-schrauben.de/cgi-bin/ ... 931-2-8-35
(on the right, click "M8x1" and then on "technische Info")

I don`t think that the 3mm less top diameter have any negative effect. But there`re also different types of bigger headed M8 bolts like i.e. this type:

http://www.online-schrauben.de/cgi-bin/ ... 921-2-6-16
(on the bottom left "DIN6921")

there`re for sure even better matches that could be used.
.... this just as an idea

G.

PS: my original piston is not magnetic and according to the colour it`s out of brass, this just as a sidenote

PascoPaso · Post by **PascoPaso** » Fri Apr 06, 2007 11:03 pm

Thanks for the info, I am on the right path now. Proitalia does not have the bearing, or the slave cylinder parts. I will check all the sites for the slave cylinder parts, maybe boring it out to some other size that is close enough so as to not affect the travel of the piston, or whatever advice is given. The button should be made out of a grade 5 bolt? Or should I find a bronze bolt/pin?

Post by **paso750** » Sat Apr 07, 2007 10:23 am

although there`s high pressure on the pin when clutch is disengaged I don`t think there`re really high forces to it. I`d just take something that doesn`t rust.
(I was in a hardware store this morning as I`m replacing about all screws and bolts of the bike and have seen stainless steel pins (securing pins for marine use) that had about ideal dimensions for being used as a replacement.)

Post by **paso750** » Sat Apr 07, 2007 7:29 pm

infact the parts manual states "bronze pin" in italian.
Not sure why Ducati used this material.
Accoring to the thermal conductivity index of materials (higher index means the material transports heat better) stainless steel would be the best. It`s index is over 50% lower than of normal steel (and steel`s index is about 7x lower than ie copper)!
A pin in material with low thermal conductivity should be better for the (life of the) bearing I`d say.

ducapaso · Post by **ducapaso** » Sun Apr 08, 2007 5:33 pm

I must say i'm disaccording with paso 750 for two reasons:
The design is incomplete.
Under the flat top there's another small step, due to make the pin discharge the pressure only in the inner ring of the bearing. I don't remember the exact measure, you can draw the diameter of the inner ring itself for about 0,5 mm thickness.
You need a "soft" metal for this work.
Stainless steel will "grind" the clutch plate every time it'll start spinning , moreover, if the pin can't scatter the heat, it'll start "burning" and create big damages to the whole clutch!

Bearing are built to face a 120° celsius temperature, this means copper is a good material for the pin

Have a nice work, Nicola
Yel "dukess" 751582
Red "smooth" 753349

Post by **paso750** » Sun Apr 08, 2007 6:18 pm

There`s no step on my piston. The 16mm diameter covers the inner ring of the bearing and a bit more, it does of course not touch the outer ring. I have 2 used spare covers incl. the pin and they are all the same.
(could be that your`s is different. Just this afternoon I had 2 lower triple clamps in my hands. Both from 750 Pasos, but both different. One had the 2 bolts on the side, the other one in the front)

That with the soft metal makes sense, I was thinking of something like that also. Regarding material atrributes of different metal types I don`t know that much I admit that, but copper heats up faster than steel, doesn`t it ? According to the heat conductivity index I`d understand that when the clutch is disengaged a bronze pin would conduct the heat better towards the bearing. Is this incorrect ?

ducapaso · Post by **ducapaso** » Sun Apr 08, 2007 6:47 pm

Yes, bronze heates quicker than steel, but the pin will still reach lower peaks ot temp than steel, because of dispersion...
Also metal expand because of heat and an unexact measure of the pin can create an interference with the inner ring of the bearing.
Actually I cannot suggest you the right clearance between pin and ring. This might be 0,1 or 0,2 mm (machine the pin 7,9mm) but you'll better measure the pin with a centesimal meter tool

ducinthebay · Post by **ducinthebay** » Mon Apr 09, 2007 5:44 am

On your mark,
Get your checkbook ready,
Go bid.

I am in no way related to this but couldn't pass up sharing this.
A brand new, unopended, piston with loose balls and all, on Fleabay.
Item number: 120106464321

I have a spare, so I won't be in on this bidding war. Good luck.

Cheers,
Phil

Post by **paso750** » Mon Apr 09, 2007 8:05 am

Nicola, thanks for the explanation.

The clutch piston on ebay is for a 907ie. I don`t think it is identical to the 750/906 part as the 907ie has the clutch piston on the other side of the engine, not in the clutch cover.

persempre907 · Post by **persempre907** » Mon Apr 09, 2007 9:52 am

Gerhard,
really, the last 906 had the slave cylinder on the left side, as the 907 and the modern Ducks, while the first 906 (like the one I had got) had it on the clutch cover like the 750.
Ciao

Clutch Piston

Piston for sale