Front Brake Master Cylinder for Honda CB650C/SC CB750 CB900C Custom Nighthawk
Updated June 16, 2026
The front brake master cylinder is the hydraulic control unit that converts the mechanical force from the brake lever into hydraulic pressure to actuate the brake calipers. It mounts on the handlebar and contains a reservoir for brake fluid.
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How It Works
When the brake lever is pulled, a piston inside the master cylinder compresses brake fluid, sending it through the brake lines to the caliper. The built-in reservoir ensures a constant supply of fluid. A waterproof brake switch is integrated to activate the brake light.
Common Failure Symptoms
Symptoms of a failing master cylinder include a spongy or soft brake lever, brake fluid leaks around the lever or reservoir, reduced braking power, or the brake light staying on or not activating.
Installation Notes
Installation involves removing the old master cylinder, transferring the brake switch and lever if needed, and bleeding the brake system to remove air. Ensure the reservoir is filled with DOT 3 or DOT 4 brake fluid and that all fittings are tightened to manufacturer specifications.
