Installing master cylinder pistons

A

Andy Mac

Full member
Hi everybody,

I am finally getting to the SFC1000 assembly stage after a many unexpected delays and setbacks, both personal and bike related.

I am about to assemble the m/cyls with new pistons/seals.  As the seals are the skirt type, I would prefer to use an insertion tube of sorts to avoid them catching on the cylinder lip, but there is little room and I cannot find a suitable tube.  The assembly instructions make no mention of having to compress the seals; either that has been missed or it is not an issue - hopefully the latter.

Any advice would be very welcome.

Regards,

Andy
 
Andy,

I faced the same situation when I rebuilt the M/C on my 3CL.
Had to have a friend turn an alloy tube to drive the seal in safely.

HTH
Gerald
 
I have a copy of a tool that was made by Richard Slater many years ago to install the seals on 15mm Brembo master cylinders. It is simply a piece of round bar bored to specific depth, with ID and OD making a sleeve to drive the seal to exactly the right depth. Bill McCracken was interested in making some copies but we don't see too much of one another these days. If anyone's interested I do have a CAD drawing. Could easily be modified for SFC1000 master cylinders.

Ken
 
The edge of the bore should have a fairly rounded edge and lots of brake assembly lube/grease has worked ok on the ones I've done. The tool for driving the retainer is a piece of tube 19.1mm ODx15.75mmID about 100mm long[measured off the tube I got from Bev Hev along with the m/c kit]. A careful little wiggle should get the seal into the bore without too much pressure.
 
Bevelheaven sell them

http://shop.bevelheaven.com/detail.aspx?ID=42

I used a section of tube cut from some long handles secateurs that was the right diameter - pure arse that they were lying around within my line of sight and the tube was the correct diameter.
 
If you just go to your local rural/farm emporium, you will find a nylon hose coupling in the correct size which is perfect for this job and costs sfa. 
 
Andy,

no need for the tube, if you take the old seals and washer as a distance piece. See my instruction PDF on the How to section.

or directly go to the archive: http://laverdaforum.com/gallery/albums/userpics/11278/Repair_Guide_Clutch_and_Brake_Master.pdf
 
Davo said:
Bevelheaven sell them

http://shop.bevelheaven.com/detail.aspx?ID=42
Click to expand...

Davo,
That is the tool for crush washer installation, it is not a lip-seal compressor.
It looks the same as my own custom made crush washer installation tool - a bit of beburred tube!!!!!!!!
I think they are being a bit cheeky there.
As far as I can tell the crush washer assembly just keeps crap out so that the piston seals can do their work without contamination.

As for using a lip seal installation tube, in pure engineering terms such a thing is desirable as the chance of damaging the seals is minimal.
The tube needs to polished inside to roughly the same standard as the Master Cylinder otherwise that defeats the object, and no sharp edges!

I didn't use such a thing for my M/C's (naughty).
I am mostly with Wdietz, a bit of care when putting the piston in with a very small amount of lube grease and no damage done. It is vital that there are no sharp edges.
I believe that some don't use grease, but smear brake fluid on the piston and seals before assembly.
With excess grease there is a risk that the smallest hole in the M/C bore becomes blocked with grease and makes bleeding a pain. It didn't happen to me - maybe I was lucky?
 
SimonR501 said:
Davo said:
Bevelheaven sell them

http://shop.bevelheaven.com/detail.aspx?ID=42
Click to expand...

Davo,
That is the tool for crush washer installation, it is not a lip-seal compressor.
It looks the same as my own custom made crush washer installation tool - a bit of beburred tube!!!!!!!!
I think they are being a bit cheeky there.
As far as I can tell the crush washer assembly just keeps crap out so that the piston seals can do their work without contamination.

As for using a lip seal installation tube, in pure engineering terms such a thing is desirable as the chance of damaging the seals is minimal.
The tube needs to polished inside to roughly the same standard as the Master Cylinder otherwise that defeats the object, and no sharp edges!

I didn't use such a thing for my M/C's (naughty).
I am mostly with Wdietz, a bit of care when putting the piston in with a very small amount of lube grease and no damage done. It is vital that there are no sharp edges.
I believe that some don't use grease, but smear brake fluid on the piston and seals before assembly.
With excess grease there is a risk that the smallest hole in the M/C bore becomes blocked with grease and makes bleeding a pain. It didn't happen to me - maybe I was lucky?
Click to expand...

Teach me to read. Mind you I never even thought a "lip seal installation tool" was required as the neither the Guzzi workshop manual nor the instructions that came with the repair kit mentioned needing one when I replaced the piston and seals on the Le Mans.
 
Thanks very much for the advice chaps.

Lothar, your illustrated instructions are really excellent - clear and accurate - Mr Haynes take note! 

I will give it a go with plenty of of lubricant - the m/cyl seal fitting that is!

For installing the crush washers I had already found that from the Draper 'Expert' double depth, bi-hex socket range, a 14 mm for the 15 mm front m/cyls and a 12 mm for the 12 mm rear were perfect for the job.

Now just the rest of the bike to build before summer's over.......hmmmmm......but not before more questions I am sure.

Cheers, Andy
 
A note of caution perhaps? I had a Brembo front m/c which had been reconditioned professionally fail at 90mph on the motorway a couple of yours ago...I will not be reconditioning again and replaced with a very nice looking Grimeca unit which is much better than my reconditioned Brembo ever was. A car mechanic, also a biker, I talked to t'other day said that if you talk to specialist brake guys, they will never recommend reconditiong..mainly because the bore will be worn. I really don't know if that is right...but  do know I don't want that heart stopping failure again for want of a few more quid being spent.
Nick7
 
No problem reconditioning master cylinders but bore wear and condition must be a consideration when deciding whether to repair or replace,... there are professionals and there are professionals, some only take the money, others also take the responsibility...
  Speed limit on the motorway is 70mph Nick  ;)


  Keith.
 
I had my rear master cylinder re-built by Ray at Motalia bout 18 months ago..He supplied the kit and the labour element was ? 10.00 + vat.

It has worked perfectly since. He did comment that there is a type of fungus that grows in the bore and has to be removed or you wil get premature seal failure after re-building.

I have rebuilt lots of master cylinders over the years without issues and providing they aren't scored or over worn I don't see any reason not to.

joe
 
Nick,

Did you find out the mode of failure?

It is Ok to buy a new unit, it will always work, but there would always be that nagging thought in my mind about what went wrong and was it avoidable.
 
Simon,
No but still have it all ..not sure I would really be able to judge...and I'll be takin' no lectures on speeding from you Mr (very lucky to still have licence) Nairn ;) Suffice to say, your life depends on those brakes, so choose your repairer wisely (mine wasn't Keith btw, or Motalia) Me, I'll not be going the recon route again.
Nick7
 
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