Brake master cylinder diaphragm busing

[aquamantx]

Who did you order the kit through?

[DEEBS11]

..........

[cajun31]

..........

If you will notice in the description of what this kit fits it specifically states it does not fit the 81 Midnight Special, which it doesn't. The only place that I found that supplies the parts needed to refresh/rebuild the rear master on the 81 LH is from Xj4ever.com

[aquamantx]

Thanks for the info. The folks over at XJ4ever are helping me sort it with a kit. Great place for parts and great people to work with. The one year off bikes are fun to find parts for.

[cajun31]

The specific kit they carry is HCP26520. You can search for it in their catalog, which is thorough but hard to navigate, at XJ PARTS CATALOG, SECTION J: BRAKES Rear Brake System Parts
Description on their site:
HCP26520 Aftermarket rear MASTER CYLINDER BASIC REBUILD KIT for all 1981 XS1100 Midnight Special models. Contains both fluid seals, the c-shaped piston retainer, the retaining snap ring, the plunger rod rubber dust boot, a glass fluid level sight window (requires the use of our HCP3120 or HCP3120A sealant for proper installation), and a packet of brake assembly grease. Note that you will need to re-use your original piston and return spring, which are not included.
$ 89.95

[DEEBS11]

Does the 81 have linked brakes? They all seem to have the same MC.

[cajun31]

Does the 81 have linked brakes?

81 LH still not covered by this kit. The LH is a unique animal. It does have linked brakes. The rear and front left caliper are actuated together by the rear master. There is also a proportioning valve linked from the master that plays a factor in how much pressure is allocated to the front and back calipers. The rear on this setup is not the same as other year rear master's. Probably why no one does a kit for it. Chacal over at XJ4ever addresses the parts needed for a refresh with the caveat being you have to reuse the rear master piston and return spring. If those are toast then you have to find a replacement, which we all know are getting harder to find.

[DEEBS11]

OK. This is the exact part number (edit: For all other models). Must be larger for linked brakes (LH).

[DEEBS11]

..........

[DEEBS11]

I think that diagram might be wrong. It does not show the front brake line. Must be a typo. (edit: Midnight Special is the LH version with linked brakes)

[cajun31]

..........

It is different and is a different part number. Yamaha Motorcycle 1981 OEM Parts Diagram for Brake | Partzilla.com

[DEEBS11]

Oh...LH! Got it.

[aquamantx]

Yes the brakes are linked.