Front disc brake master cylinder

The front brake master cylinder and its reservoir is fitted to the front brake handlebar-mounted lever. It is located to the handlebar by two alien screws. When removing it is not necessary to drain the hydraulic fluid unless it is to be removed away from the machine; the reservoir's cap is good enough to keep the fluid sealed in. Never hang the master cylinder/lever on the hydraulic pipe which goes down to the distributor block under the lower fork yoke. Hang it with an elastistrap.

To remove the master cylinder for overhaul, loosen the hydraulic pipe first, to obtain purchase. Its banjo bolt will be hidden under a rubber moulding to the right of the speedometer on some machines. Once the cylinder is free, be ready to mop up any hydraulic fluid from the pipe and reservoir. Take off the reservoir cap and pull out the rubber inner seal — it sits on top of the fluid surface. Drain out the fluid and clean the whole unit with methylated spirits.

Detach the lever which pivots on a chrome screw and lock nut. The screw also threads on the master cylinder body. It is now possible to release the piston, seals and springs through the master cylinder body and out at the point where the lever would press.

Mote the order of components and then check their conditions. If either the piston or cylinder 15 badiy scored, then a new master cylinder will be needed. If both are clean, replace using a new piston with its spring with new seals; never re-use seals. Brembo's special tools are required for easy replacement. Soak the cylinder, pistons and seals in clean brake fluid before installation. (It is mown that these master cylinders do wear fairly quickly which means that their condition should be checked, at least, every three years if no other symptoms appear).

Reassemble all the parts, install the master cylinder, top up with brake fluid and bleed the system. Some levers use little alien screws to adjust lever-to-piston free play. Use Locktite in its thread and adjust to suit. When installing the cylinder to the handlebars make sure that the hydraulic pipe does not abrase the speedometer mounting and that the lever can travel through its full 'grip' without touching the twist grip body. Do not overtighten the lever when installing.

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