Early coffin brake master seal replacement?

[Mr Gazza]

Hope someone can help me out here... I'm stuck!

I have a very early coffin type brake master, 13mm for single disc (It is possible that it isn't originally from a Monster).

I have a brand new Brembo seal kit and all the components that I can compare seem identical and correct for the master I have.

Here's the problem. I was expecting to see a circlip with holes for circlip pliers, but this is not the case. I see a retaining ring in the bore with no visible means of removing it.
There is a new ring in the kit which looks dimensionally identical to the one trapped in the bore, but no clues as to how it would be removed, there is no break in the ring. There is a shallow external annular groove which could potentially engage on a wire clip, but that would be an impossibility really?

Instinct tells me that it should be knocked out from behind, but the only access to that would be the tiny 2mm? hole in the banjo end of the master. it would have to be knocked out with an O-ring and plastic ring. I don't think they would transmit any knock!

Any clues please? Am I in need of a special tool or a special person to do it for me..?
Looking like a precise tubular drift to push it back in again too, with the rubber boot in place.

[Luddite]

I'm not sure if this is of any help, Mr Gazza, but Bevel Heaven list a special tool for inserting the replacement seal:
http://www.bevelheaven.com/stuff-for-sale-brembo.htm



They describe the seal as a "crush washer", which suggests it might just be a tight interference fit rather than located in a groove. Can you get a right-angled engineer's pick behind the washer to 'hoik' it out?

[Mr Gazza]

Thanks Luddite... you're a star.
That's thrown a little light on the matter. At least it confirms my suspicion about the putting in tool.

I'm trying to think of a way to hook behind the ring and apply a slide hammer to it.
I inherited a lovely slide hammer that Jeff made for the Commando, but so far a design for a hook is eluding me. I feel the need to pull on opposite sides of the ring for a nice square pull...Something resembling scissors is forming in my mind.. Not sure I have the technology Captain?

[Luddite]

You may well be able to drift it out from behind using a thin punch. I found this guide on the Laverda forum where a 3mm drift was used. It's not a coffin-type m/c but the piston retaining method appears to be the same.

https://laverdaforum.com/gallery/alb...ake_Master.pdf

Here are some extracts:









Hope it helps...

[Mr Gazza]

Thanks again Luddite.
Unfortunately I don't think punching it from behind will work. the hole in the "Back" end is tiny, about 2mm or less. Then I will have to punch against an O-ring, a plastic washer and the remains of the rubber dust shield.
My master is configured differently to the Laverda one, as the piston is not retained by the ring...It fell out.

It's tempting to drive something sharp down the side of it and then fold it in on itself, but the risk of damage to the bore seems quite high. These masters are getting very rare, so I want to tread carefully.....Then there is the clutch side to tackle.

[stopintime]

Get two new? Less than 100 each...

[Mr Gazza]

Are you going to treat me to a pair then stopintime?..

Cheapest new I have seen were £145 each, and not even the small reservoir type that I want.

[stopintime]

Amurican OPP Racing has the 13mm with small coffin, microswitch and lever for ~87 GBP.

More if you pay VAT....

[dacs]

Mr Gazza, it might be worth a call to Powerhouse. Their ad only mentions caliper overhauls but worth a try. Contact details on www.powerhouse.uk.

[Mr Gazza]

I can get clutch and brake masters complete from China for about nine quid a piece, but I already have the masters I want.

Dacs, cheers for the info...I'll probably go to Carl Harrison if the impasse remains.

[utopia]

Gazza .. I'm sure I don't really need to say this but if you need a special drift or some other tool making, just let me know.
As long as it can be done on a lathe.

[Mr Gazza]

Thank you Jeff, I'll let you know.
I have a selection of tubing to look at in the mean time, possibly even a socket will do the trick. The hard part is getting the ring out.
I have discovered that the ring is steel.

[bobbertandsammy]

Watching this with interest as I was going to rebuild the clutch master cylinder on my 750 this weekend.

[Mr Gazza]

To update this...

Last night I decided to get serious with this pesky little clip/ring.
I found an old pair of scissors in a first aid kit and ground the outer edges into fine hooks, with the intention of getting the hooks under the ring and pulling the scissors open and up.
This worked to some extent as it was successful in removing the remains of the rubber cap from under the ring, but I couldn't pull hard enough to shift the ring even with the scissors nicely located as designed.
I remembered Carl Harrison's advice of trying a little warmth and just prising it out. So I stripped everything out that might get damaged by heat.. The switch and plastic level window. I warmed her up and just levered the ring out with a screwdriver...Simple as!

Now for the bad news! I discovered that there is a little "pushrod" or "button" that slips in the master body and makes the connection from the lever to the microswitch, as the tiny little button on the switch will not reach the lever. Put it this way, I discovered it, due to working out that it was missing after removing the switch.
Although it must be a small black cylinder about 10mm long and 4mm round, I can't find it, even in my reasonably clean workshop... It could have gone in any direction unseen and unheard!!

So, a big ask of anyone who can help with this. Does anyone have a spare one of these little "buttons"? I will gladly pay your asking price if one is available.
I am initially thinking this would be an easy part to have 3D printed, possibly in multiples.
So if I could even have the loan of one it would be fantastic as I could measure and draw it, the rest is simply a matter of a few emails and these would be cheaply available to anyone.

Thanks in advance.

[Luddite]

You're certainly not the first to suffer this way, Mr Gazza. Is this the part 19540021A:



I think others on here have fashioned replacements using biro refills or aerosol tubes (5mm long if memory serves).

If you wanted to order one or more from Moto Rapido, I'd be happy to pick them up and post them to you as I don't think MR will post things below a certain value.