RGS rear brake master cylinder seal kit

parrishsteve

parrishsteve

New member
Location
Chicago, IL USA
Hello friends,
I ordered a rebuild kit for the rear master cylinder on my 1984 RGS1000. I was shipped a brembo rebuild kit #110279720 for the 12mm master cylinder. But the piston looks like one for a front brake. The original piston for the rear MC has a cavity for the rear brake pedal push rod. I'm assuming that I really don't have the wrong kit but rather I'm expected to transfer the 12mm seals from the new kit and retrofit to the old piston. Does this sound like something a Laverda owner would need to do? :)

Thanks and have a great day!
-Steve
 
You do have the wrong rebuild kit, but I'm unsure if PS12 rear m/c rebuild kits are still available. Swapping seals on your original piston is an option but be aware of the risk of seal damage when attempting this. Brake system integrity is a critical safety requirement.
 
The rebuild kit you have is for a SFC1000 which is the same size as a RGS ( 12 mm ) but the piston is different. The correct kit for a RGS is obsolete but Andy Wagner still shows them as being available and expensive! Luckily the piston seals you received are the same so you can put them on the RGS piston.

If you received the rebuild kit from Wolfgang, it's probably because he no longer has any RGS rebuild kits and expects you to swap the seals.
 
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@1200ts Yep, I got the kit from Wolfgang, he's on holiday so I didn't want to bother him. I just wanted someone to help me confirm that, more than likely, I need to transfer the seals. So that's my plan. @Rob I hear ya! They are little things but the seem pliable enough so I will attempt to carefully transfer them. Thanks guys!
-Steve
 
Steve I did this job last month on my RGS with no problems encountered. As others have said the rear PS12 overhaul kit for the RGS brake is no longer available so I re-sealed the original piston with seals from a PS12 front master cylinder overhaul kit. Use a squirt of WD40 to keep the seals lubricated and minimize risk of damage.
 
Laverdian said:
Steve I did this job last month on my RGS with no problems encountered. As others have said the rear PS12 overhaul kit for the RGS brake is no longer available so I re-sealed the original piston with seals from a PS12 front master cylinder overhaul kit. Use a squirt of WD40 to keep the seals lubricated and minimize risk of damage.
Click to expand...
Not sure WD40 compatible with brake fluid. Hopefully such a small amount you'll be OK. I always use either brake grease of brake fluid as a lubricant for internal brake parts.
 
The job is done. I transferred the seals. The kit came with a little packet of grease I used to dismount and remount. It went smoothly and I have no reason to think the seals suffered any damage. However, if you hear I crashed into a wall at high speed then you know what really happened :)
 
Does anyone know the Brembo part number for the RGS 12 mm rear master cylinder rebuild kit? I am wondering what other bikes besides Laverda used this master cylinder. I have in the past found parts at other Italian motorcycle dealers ( Ducati, Moto Guzzi, Benelli and others ) that are the same as used on a Laverda. But I have no idea what part number I am looking for?

In the past few months while working on a number of Laverda triple brakes, I have learned:

SFC1000 and RGS/RGA some of which have a 14 mm front master cylinder, the master cylinder and rebuild kits are obsolete. Some dealer still have a few rebuild kits. Master cylinder is not available at all. When parts are gone your options are to bore it to 15 mm for which rebuild kits are still available or fit a different master cylinder.

SFC1000 rear master cylinder which is 12 mm. Master cylinders are not available but rebuild kits still are, at least for now?

RGS/RGA rear master cylinder which is 12 mm. Master cylinders are not available but rebuild kits are still available from Andy Wagner. Brembo also shows these as obsolete. Seals from another 12 mm master cylinder such as a SFC1000 will fit.

The 15 mm front and rear master cylinders as used on many Laverda's and other bikes are also obsolete. But rebuild kits are still plentiful and reproduction master cylinders ( made in China? ) are another option.

Calipers don't seem to be a problem although the Laverda type with threads in the caliper appear to be obsolete. So if using one from a bike such as a Ducati, you will need a longer bolt and a nut.

Those out there that know more than me, please correct all I have stated that is incorrect.
 
"Calipers don't seem to be a problem although the Laverda type with threads in the caliper appear to be obsolete. So if using one from a bike such as a Ducati, you will need a longer bolt and a nut."
...and some spacers for Ceriani forks if my experience is anything to go by. The upper and lower spacers required aren't the same width either if the one I'm doing is anything to go by.
 
1200TS
you are ignoring imperial dimensions which do come into affect here,
Ceriani forks on Laverda will require callipers with threads, and Marzochi forks on Laverda, without threads, plain callipers can be fitted with Timecerts, if you are a skilled engineer, to get the thread back, and of course threaded callipers can be drilled out, BMW callipers which look the same as Laverda PO8's, have a different offset, however Brembo four pot callipers from BMW can be used in the same way as Laverda type four pot callipers (if you can stand for or remove the "BMW" Llogo) its a very complicated subject and it would seem that Brembo are slowly stopping parts only supplies due to public liability issues, Ducatipaddy here in UK has good stocks of Brembo parts and replica parts, he is also very knowledagable. I bought a Chinese made rear master from him recently and have not looked back.
CLEM
 
What is being missed here (again!) is that the un-threaded P08 calipers usually do not have the mounting lugs machined on the (incorrect) mounting face when fitted to forks calling for threaded lugs. This results in wonky mounting of the calipers, perhaps not too critical in use, but often looks simply terrible from an engineering POV, especially with a nut fitted to the inside of the caliper.

On these later calipers when fitted to a corresponding fork, mounting bolts bear on an un-machined, as-cast surface that is rarely square to the rear machined surface of the lug. The lugs need a slight skim on the mill to get them flat and parallel and spacers to get the calipers centralised over the disc. Only then can the calipers be rigidly mounted without any stress being introduced by mounting bolts into either caliper or fork lugs.

There is no shortage of the later un-threaded type, still available new from Brembo outlets. The threaded type, in all variations, has become extremely rare, especially in usable condition.

A cheap and easy upgrade on Ceriani forks is the use of 4-pot Brembos from K- and R-models from BMW. These have identical mounts to the early P08 but different lateral spacing. This is easily corrected with a couple of spacers.

Back to the original topic, I can supply NOS PN12 M/Cs for RGS/RGA models, but no service/repair kits. These have been discontinued since almost forever... PS12 repair kits however are still available.

piet


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I've heard that some brake manufacturers don't sell rebuild kits for liability reasons. I'm not sure whether that's the true or not because there are heaps of rebuild kits of various brands on the market.

Some years ago, I needed to do a refurb on a M/C for which I couldn't find a rebuild kit in Australia. It wasn't my bike so I forget what make and size it was (14mm is a number that comes to mind and it was on a Jap bike so probably Nissin?). Anyway, I took the M/C piston into a brake and clutch parts/repair business and asked if I could have a look at some 14mm rebuild kits, then bought one that had similar looking rubbers on the piston. I didn't care what brand it was or what sort of vehicle it suited. All I wanted was the rubber rings off the piston. Swapping the rubbers from the new kit onto the old piston got the bike's brakes working again. Sometimes you just have to work with whatever parts you can get your hands on.
 
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