Airhead handlebar-mounted master cylinders
Handlebar-mounted master cylinders started in the late '70s with the R65, but became ubiquitous in 1981. This article describes the types used until the K-type controls were introduced in 1991.
Prior to this, Airheads used the under-tank master cylinder with the cable control. The throttle housing resembled the ones mentioned here, but merely pulled a cable rather than providing for a hydraulic master cylinder and had no provision for a switch.
Application
| Model* | MC | Housing | Notes |
|---|---|---|---|
| Early R65 w/single ATE caliper | 13mm 32 72 2 302 354 | 32 72 1 238 377 | Round reservoir Dual throttle cable 6x1 switch thread |
| Early R65 w/twin ATE calipers | 16mm 32 72 2 302 355 | ||
| '81-'84 single Brembo All monolever G/S |
12mm 32 72 2 302 369 13mm 32 72 2 310 784 |
32 72 1 242 563 | Square reservoir Single throttle cable 6x1 switch thread |
| '81-'84 twin Brembo | 14mm 32 72 2 310 785 |
||
| '88-'90 R100GS w/single Brembo | 13mm (as above) | 32 72 1 454 461 | Square reservoir Dual throttle cables 8x1 switch thread |
| '85-on** w/dual Brembo | 13mm (as above) 14mm (as above) |
* Years are approximate. Brake systems often changed in the middle of a model run.
** excluding '91-on R100R/M/GS
Housings
The housings changed a few times:
- Early R65 housings are shaped for the round reservoir, although the newer square ones might fit.
- '81-84 housings (and continuing until '87 for the R80G/S) were all designed for a single throttle cable.
- Original housings had small posts for the throttle cam, but these were later upsized to 15mm. Newer housings need newer cams and covers.
- Starting with the monoshocks the bikes (except G/S) reverted to dual throttle cables, which affected the housings and covers. At the same time, the front brake switch changed, bringing a larger threaded hole size.
The fiche shows the newer front brake switch as being used with new single-cable housings, but my experience is otherwise. The old switch has a 6mm thread while the newer one (with integrated cable) has an 8mm thread. The switch geometry is similar, so housings can be drilled and tapped for the newer switch if desired.
More information on the housings themselves is on this page.
