I've finally got around to re-starting project 907.

I'm stripping out the front brake calipers on my 1991 907ie.
I want to renew the piston seals.
The calipers are the black ones.
I understand that KTM sourced parts will do the job.

I'm not sure whether I need to refer to this -


http://www.ams4ktm.co.uk/ktm-parts-find ... 138&model= 970041&schematic=C94583131_970041

Or this -


http://www.ams4ktm.co.uk/ktm-parts-find ... 177&model= 972204&schematic=C99587130_972204

or something else?

All input appreciated, as ever.

I remember you asked this some time ago and looking at that old topic we all assumed you had the golden 4 piston Brembos P4 30/34C not the black ones (P4 32).
Those links don`t really go anywhere so it`s hard to tell what parts those are but from memory KTM has the seals that fit the golden Brembos.

The complete kit (pistons + seals) for the P4 32 was # 120.2799.60. (this shop might have it http://www.gawa-guzzi.de/ )

Seals only:


G.

Crikey, how ever do you manage to remember such information?
However, many thanks for your informative reply.
The ebay seal kit looks to be right, so I'll probably bite the bullet and go with that.
I must say that it is most gratifying to be back doing stuff to the 907.
I'm hoping to get it on the road and tested before the Italian bike day at The Ace café.
Watch this space!

Be cautious buying seal kits for the 4 piston calipers. The black ones were only used for a few years, so seal kits for them are going to be much more rare than the seal kits for the gold calipers, which they sold millions of. They are different piston sizes, hence different o-ring sizes as mentioned in the previous posts.

Personally, I like the black 32mm calipers over the gold calipers that came later.

Cheers, Phil

O.K. Thanks Duc.
I took apart the calipers, stripped out the seals and cleaned everything, and reassembled the calipers
I'm still not happy with the braking action though. The pistons don't seem to retract properly when I release the brake lever.
As a result, I have ordered the seal set shown in the link provided above by paso 750. (Thanks P750 )
I will post the outcome when I've done the job.

Cheers

John, I assume you cleaned the pistons carefully (mild abrasive pad, lacquer thinner or polish) and lubricated pistons and seals before assembly? Usually some kind of assembly lube or rubber grease is used which might also come with a seal kit.
As you will have cleaned the caliper halves I`d replace the brake lines if you still have the old rubber ones from 91. If they start dissolving internally it can happen that they clog under pressure and release pressure slower.

paso 750
I cleaned the brake parts with paraffin, using an old (soft bristle) tooth brush.
Yes, I did lubricate the pistons with rubber grease.
I had already changed the brake lines to a two-line set, cutting out the splitter.
These are all jobs I've done before on other motorcycles, so I'm comfortable with it all so far.
I suspect that I will eventually have to fit new discs as they are a bit rough; 'Hilly' would be an apt description, I think!
I don't mind changing the seals; I want to eliminate all other causes first, and I like to be thorough.
I'm just hoping that the master cylinder isn't a problem. My understanding is that they are not available from Ducati, and there is no service kit for them either. I would be happy to be proved wrong about the service kit, and would do that job as a matter of course if anything was available.

Ideally, I would take the bike out for a ride, bed the new pads in to the discs, and then have a better idea of how everything performs. Trouble is, I can't ride it on public roads until it has passed an MOT test. I can ride it to a pre-booked test, but any problems would only show up on the way to the test. I did that once with my old Triumph Trophy 1200. The front pads started to bind on the way to the test. I tried to get it through the test, but it failed. New caliper seals fixed it !
Anyway, I've just had an email to say that the seals are on their way to me, so I should know more some time next week.

Many thanks for your helpful input.

I find repair kits for the PS12, 13 and 15 brake master cylinder but not for the PS16.
Wonder what the difference between a PS15 and PS16 is as the piston that comes with the PS15 kit is 15,84mm diameter x 65mm length. (BREMBO REF. 110273920)
Finding a new Brembo PS16 master cylinder is not a problem at all. Maybe Ducati doesn`t have them but it seems everyone else does.

Make sure that the screw in the lever that sets the distance of master cylinder pushrod isn't in too far. If it is screwed in too far to reduce the free play the piston doesn't fully return, blocking the bleed hole that allows the fluid back to the reservoir. The result of this is that the system remains pressurised preventing the pistons from fully retracting. When it gets hot from braking the expansion of the fluid worsens the situation and can lead to the wheel locking up.

Well, the seal kit, from powerhouse-uk, via ebay, (thank you paso750 ) seems to have done the trick. There is now minimal binding between the new brake pads and the brake discs. Pretty much what I was hoping for all along.
I haven't ride-tested the brakes yet; Too cold, wet, even snowy , but I am pleased with the results so far.
I fitted the new brake bleed nipples that came with the seals, but just could not bleed the air out. When I refitted the original nipples it was all done in no time! The new nipples only have one small hole in them, whereas the originals have two .
Tomorrow I will be replacing the warped rear disc with a Ducati Monster one that I located on ebay after finding the disc-alternatives comparison list on this forum. Many thanks to the author of that information; Excellent work .

After so much of this it is most gratifying to feel that some progress is being made.

- - - - and now the rear brake disc is fitted - AND the front brake light switch!
Cripes, so much progress.
Time to start putting its clothes back on, I feel.