Master Cylinder

[Targabill]

Hi, Does anybody know if there a rebuild kit for the master cylinder? I have a 81 R65.. dual brakes. ATE calapers..
I've been pumping for ever and getting no pressure, and I get a small leak around the lever.

I've been having a hard time finding part numbers for the R65. Can anybody recommend a web site for parts.  

Bill

[montmil]

This ought to get you some parts info. Then, you can shop price and availablity using the part number. Lots of price differential out there...  

http://www.ascycles.com/Illustrated_catalog/R65(78-85)/catalog_frameset.html

Monte

[Bob_Roller]

Bill,

Just in case you didn't know this, there are two different size master cylinders, the daul caliper setup on the '81 model year is I think a 15 or 16 mm, the single disc master cylinder is 12 mm.

The size is cast into the bottom side of the m/c.

Don't know the history of your bike, but you may want to take the m/c apart before ordering the replacement parts, and see if you have corrosion damage to the aluminum bore where the seals ride.

Not too uncommon to find this causing leakage.

[Yikes]

Max BMW is another good source of parts with an excellent fiche to browse through:
http://www.maxbmwmotorcycles.com/fiche/MainDiagrams.asp?mospid=47851

I got my rebuild kit from Chicago BMW, who are priced right, but can be a bit slow:
http://chicagobmwmotorcycle.com/store/

The rebuild "kit" consists of a new plunger, spring and washer.  Not much for the $40-$50 cost, but it is a pretty easy fix.  Don't be like me and wait until the dripping brake fluid ruins your front fender finish to do it.  Good luck with it!

John

[Bob_Roller]

From the looks of the parts catalogs for the R65, it doesn't show the rebuild parts.

I did a search on the R100 for the same model year ('81), and found that the larger bikes used the larger master cylinder (16 mm), part number for the kit is :32722302357, cost looks like $55, Chicago BMW has it for $44.

Complete master cylinder (16 mm), part number is : 32722302365, cost $171, Chicago BMW $137.

Chicago BMW has had the reputation for slow service at times, so if you do choose to do business with them, keep this in mind.

I had to replace my master cylinder in '92 due to corrosion, saw an ad in Hemmings monthly auto listings for a company called White Post Restorations in Whitepost VA., that would bore out the master cylinder, and install a brass sleeve, gauranteed never to corrode again, cost was around $75 in '92 ( I'm sure it's gone up since then !!!).

http://www.whitepost.com

[Justin B.]

Bob, I've been thinking about trying that on an old cylinder I have laying around here and also turning a new piston out of stainless but I don't know of a source for just the rubber bits.  If we could just source the piston seal we'd be in business.  I have no idea why the kit only comes with a new piston as the old ones I've removed looked OK.  They could have just done a kit with a new spring and rubber bits for about a ten spot...  

If I remember correctly Stainless Steel Brake Corp. will sleeve them with stainless steel, at least I think they used to.

[mikethebike]

'81 on cylinders have various sizes as shown here:-
http://www.bmwandguzzispares.co.uk/bmw/products/product.php?f=i&code=BA_15_20_HA_35&shnew=New&model=R45/50/60/65/75/80/90/100%20(2%20valve)&shnewcode=15&part=Brakes&sub_part=Master%20cylinder%20and%20parts%20(Brembo%20and%20Magura)&modelcode=20&partcode=HA&source_code=BA_15_20_HA_35&spPage=2
on Motorworks website. Hope this helps,
Mike

[Rob Valdez 79 R65]

I ordered mine from Matt at Boxerworks.

[MrRiden]

I'm thinkin' that the rubber bits should be of a standard design & size not unlike our bearings and seals. [BTW did any of Monty's seal / bearing specs make it into the permanent tech section?] I'm sure a search of industrial supply catalogues would turn up an off the shelf replacement.
rich
planning a search of Thomas Register

[Targabill]

Thanks for all the info.. I do have the 16mm cylinder. Does the piston just pull out, after removing the curclip? It would be nice to just order the rubber....

thanks,
Bill

[Bob_Roller]

Bill,

It should pull out, but it's been in there for 27 years most likely, so a little muscle may be necessary to remove it.

[Justin B.]

Rich, I used to machine at a hydraulic shop and I know the guys that rebuilt the cylinders had books/catalogs with every conceivable seal and gizmo you could imagine but I no longer have access to that.

[Yikes]

On my rebuild, pulling the plunger out of the master cylinder after the circlip wss removed was not really too tough.  The real challenge was removing the master cylinder from the throttle body to get at it.  After 27 years of being together, mine just did not want to separate.  

[montmil]

I'm thinkin' that the rubber bits should be of a standard design & size not unlike our bearings and seals.... I'm sure a search of industrial supply catalogues would turn up an off the shelf replacement. rich planning a search of Thomas Register

This is a massive catalog with everything you might need to rebuild after the apocalypse, or maybe a tsunami, tornado, quake, whatever.

My personal theory is that those peeps who have tools and can use them; fix toilets, electrical circuits, engines, etc, other than working all day on a compuKer, will become kings! Maybe.    Monte

http://www.mcmaster.com/

[Targabill]

I popped the MS off, and pulled it apart.. The rubber is ripped, hense the leaking. The inside of the cylinder has some pitting but it's very close to where the curclip sits and the rubber doesn't pass over it. Down in look OK, but can they be honed out. or is it worth getting a whole new MS.. It's only $93 more then just the piston. But, if I can buy just the rubber....... Humm