Typically, all motorcycles from the 1970s and 1980s had brakes castrated by master cylinders with far too big bores and pistons. It was like lifting a heavy stone with too short a lever- pressure on the brake lever resulted in far too little pressure on the brake pads and only Arnold Schwarzenegger could get the disc front brake of a Commando to work. Add to it a wooden feel which allowed for no metering of the brake force.
Over the years many rectifications were tried with different calipers attached by unsightly and often off-line adaptors. The real cure, however, is to reduce the bore of the master cylinder and the diameter of the working piston.
Several re-sleeve kits are on the market but so are the reports of sleeves working loose and turning, thus blocking the holes for the brake fluid, resulting in no brake or, probably even worse, front brakes locking up.
We have, therefore, undertaken the manufacture of new master cylinders with smaller bore (13mm) for pre-850Mk3 Commandos and 850Mk3 Commandos .
For those who have the original master cylinder we have a "kit" for 750/850 models.

Given the 850Mk3s often have brake levers from different forging tools plus seem prone to wear we do now solely offer complete master cylinders for this model.