87 Master Cylinder Rescue

[pehayes]

Hand brake master cylinder on my '87 SPII started a gentle leak.  I was warned that rebuild parts are NLA.  The same 'trapezoid' master cylinder is used on various bikes in the lat 80's early 90's.  Someone advised that White Post Restorations in Virginia could restore anything by re-sleeving and fitting other piston parts.  Estimate in the hundreds!  I sent them the mastery cylinder.  After a month they said they couldn't find appropriate internal parts.  I asked them to send it back and they charged me $26 for return shipment.  ???

Meanwhile I found a Guzzi parts vendor in Sicily who advertised a rebuild kit.  I have friends in Italy.  I asked one to buy a kit for me and send it along.  Includes seals, split ring, spring, washer.  45 Euro plus 5 Euro to post it to my friend and another 5 Euro for him to post the kit to me.

Direct replacement.  Installs and works just fine.  My cylinder bore was without damage.  The reservoir cap has a complex gasket and those continue to be obsolete.  Sheet rubber substitution is possible there.

The kit is part number 28659300 "Gruppo revisione pompa".  See here:
https://www.motogiovane.com/mobile_product_info.php?cPath=67&products_id=772

Then vendor in Italy is MotoGiovane:
https://www.motogiovane.com/contact_us.php

Will they sell and ship directly to you?  I don't know.  Wasn't worth the language hassle.  I just imposed on local friends.

Patrick Hayes
Fremont CA

[guzziart]

Good!  It beats re-sleeving if the pump bore is good. 
I've resigned myself to to modifying the MC asm to accomodate a remote reservoir like new bikes have when the trapezoid reservoir gasket finally coughs its cookies.  I rebuilt the assembly in 2010 with new seals for the pump & reservoir (Moto Intl) but suspect those items were at least a decade old when I intalled them.  If I could get my little hands on a fubar trapezoidal pump assembly I'd mock it up to accept a remote reservoir.  About a year ago I had bought one on ebay but then the vendor told me that they could not find the unit in their inventory.  At another point in time, an acquaintance here offered to sell me a servcieable assembly but I could not in all good conscience take a good assembly and modify it past the point of no return.  Anyway, I'll keep on the look out for a good modification candidate pump assembly.
Art

[Cdn850T5NT]

Good!  It beats re-sleeving if the pump bore is good. 
I've resigned myself to to modifying the MC asm to accomodate a remote reservoir like new bikes have when the trapezoid reservoir gasket finally coughs its cookies.  I rebuilt the assembly in 2010 with new seals for the pump & reservoir (Moto Intl) but suspect those items were at least a decade old when I intalled them.  If I could get my little hands on a fubar trapezoidal pump assembly I'd mock it up to accept a remote reservoir.  About a year ago I had bought one on ebay but then the vendor told me that they could not find the unit in their inventory.  At another point in time, an acquaintance here offered to sell me a servcieable assembly but I could not in all good conscience take a good assembly and modify it past the point of no return.  Anyway, I'll keep on the look out for a good modification candidate pump assembly.
Art

@guzziart, regarding a remote reservoir, I assume the only important thing is that said remote reservoir be mounted in a manner, however remote, at a higher elevation than the master cyl? The hose could go all over h*ll's half-acre, up, down, and around... but the res would ultimately have to be higher? Like, say, mount it on the LH handlebar?

If my suppositions are right, then the only complication would be that gravity bleeds are out... power bleeds the order of the day?

[guzziart]

Hi CDN,

Yeah, the rez definitely has to be mounted higher than the pump.  The concept I plan to use mimicks what is on sport bikes today or like what came on my V11 Lemans.  No, it aint gonna be mounted it on the left hbar, it'll be within an inch or two above of the front brake pump on the right. And, no fancy shmancy bleeds required. 

I'll document as best I can in the WGC restoration area once I get started.  I know of at least one other fellow that has a leaking trap reservoir that has made the bike unuseable, fortunately mine is not there yet but I'm sure one of these fluid change days it won't reseal.  Thanks Brembo.

Art

[Cdn850T5NT]

Thx @guzziart. Seems to me that with the right durometer- and thickness of EPDM sheet material, the bolting torque can be applied just right to seal on this sheet of EPDM (cut-to-size) as a replacement top gasket. The issue CAN be that brake fluid leakage occurs on the bottom plastic reservoir o-ring, the cast material that the plastic reservoir resides-in acts as trough for the leaking brake fluid, and then the extremely small Allen-head screws rust in place into the aluminum housing, because the pool of brake fluid they are immersed-in attracts atmospheric moisture... Then, the only POTENTIAL way to unstick said extremely delicate rusted screws is to remove the whole assembly intact, turn it upside down, and attempt to dose said screw-ends from underneath the aluminum casting (while it's upside down) - with quality penetrating oil. The drillings are done clean-through to the underside of the castings.

[guzziart]

I've not had problems with the screws corroding in the pump housing threads nor leaking from the reservoir oring which I think could be matched up/procured locally at a bearing supplier, Mcmaster-Carr, etc.  I've already decided I do not want to attempt to duplicat/fab a replacement diapragm.  Had I been successful with Brembo and their aftermarket group at getting my hands on on an engineering drawing for that mess I would have tried to get the diaphragm produced/re-produced.


Oh well.



PS - Geez, I hope you didn't have to go through the screw removal process you described with great detail!

[Cdn850T5NT]

No, I have not had to go through that bother...

However, thinking this through a bit, my idea re the EPDM sheet would not work... unless the following were done...

The top seal of the reservoir has to have the ability to collapse-down with a reduction in reservoir level, or else the vacuum created in the airspace above the liquid level would impair fluid from flowing in to the master cylinder as the brake lever is operated.  Now the fact that the OEM top gasket is "articulated"... that allows it to do that. Here is an alternative... that is not as good as OEM ('cuz the fluid is fully vented to atmosphere, and can/will take-on moisture, and therefore needs flushing say every 2 years)...

Fashion an aluminum top cover for the reservoir...

Drill and tap it 1/8" npt at the centre of it...

Take the appropriate EPDM sheet and cement it to the underside of the new aluminum cover. Use a cement that is compatible with brake fluid.

Make a puncture of the EPDM sheet where the drilling/tapping is...

Pipe-away vent tube so that any brake fluid that makes its way up the tube cannot leak out... and moisture/rain cannot leak in. And then add a "vent" hood, vertically-oriented...Or use a vented male-NPT differential- or transmission vent fitting directly on the aluminum reservoir lid if you can assure yourself no rain could leak-in.

[ridingron]

What am I missing? Looking stock obviously not an issue. Spend some time on ebay. Find a MC with a similar bore the fits the handle bars and the banjo bolt. Buy it, clean it up, rebuild it (if you think it needs it), install it and go ride.

[Cdn850T5NT]

What you're missing is that all of the switchgear and the throttle assembly is integral with this unit... so it behooves a person to make it work...

[dguzzi]

    Maybe, just Maybe...you could try Tim and Tom at Wheels Unlimited in Rochester, Mn.  I've been able to find Brembo stuff from them for my '87 Alazzurra.
Phone is 507-288-5630  Very nice guys that will try to source what you need.

[Cdn850T5NT]

    Maybe, just Maybe...you could try Tim and Tom at Wheels Unlimited in Rochester, Mn.  I've been able to find Brembo stuff from them for my '87 Alazzurra.
Phone is 507-288-5630  Very nice guys that will try to source what you need.

Many thx for the lead!

[guzziart]

    Maybe, just Maybe...you could try Tim and Tom at Wheels Unlimited in Rochester, Mn.  I've been able to find Brembo stuff from them for my '87 Alazzurra.
Phone is 507-288-5630  Very nice guys that will try to source what you need.

Thanks DG, I'll give'em a call!  The last time I was able to get these parts for my '87 was in about 2011 from Moto International and they told me I probably got the last reservoir rebuild kit in existence....I wanted to buy two but they only had one.  AFAIK, the kit I bought back then may have been sitting on their shelf for a decade or so.

Art

7/9/23 UPDATE:  I called Wheels Unlimited yesterday and they were regretfully unable to help.

[Roebling3]

Quality Remanufacturing.  Marion Szotak   973-523-8800.  565 E. 37th St.  Paterson, NJ 07513-1179.

It's been a long time since I've done business with them. They have/had the magic. Clutch and brake systems, calipers & pumps vacuum and air pumps, windshield air-motor pumps, suspension systems, as in shock absorbers.   R3~

[Cdn850T5NT]

R3, something tells me I've heard of him before, somewhere. Fine machinist, watch-maker-like finesse...? Worth a try... a tradesperson who "could fashion shoes for a house-fly" (an old Veneto saying). Cool.

Another thought re the top bellows-like gasket:

Not saying THIS specific one ('cuz of the non-flat/ridgelines) but a jobber piece like this could possibly be found...  ???

Of course it'd 'hafta be cut to size, and that aluminum replacement top-plate'd 'hafta be fabricated (I would think).

[dguzzi]

Thanks DG, I'll give'em a call!  The last time I was able to get these parts for my '87 was in about 2011 from Moto International and they told me I probably got the last reservoir rebuild kit in existence....I wanted to buy two but they only had one.  AFAIK, the kit I bought back then may have been sitting on their shelf for a decade or so.

Art

7/9/23 UPDATE:  I called Wheels Unlimited yesterday and they were regretfully unable to help.

     
 
   Ok, it was worth a try....  Thank you for letting us know.