How to Seal Motorcycle Brake Fittings

Motorcycle brake lines are highly engineered components that perform several important functions. They form the link between the master cylinder and the brake caliper piston. The lines are built with braided metal filaments surrounding a rubber inner line that supports the hydraulic pressure from the master cylinder and prevents the line from expanding. Metal fittings are swaged onto the ends of the line. These fittings are usually machined with a "phonograph finish" that leaves a pattern of small ridges. These ridges bite into the crush-washers used to seal the connection to the calipers and the master cylinder.

Things You'll Need

• Shop rags
• Phillips screwdriver
• 12 point socket set
• 3/8 inch ratchet
• New crush-washers
• 3/8 inch torque wrench
• DOT 5 brake fluid

Instructions

1. Wipe the master cylinder with a clean rag. Remove the screws in the the master cylinder cap with the Phillips screwdriver. Place clean rags around the master cylinder and the brake caliper(s) to catch any leaked fluid. Remove the cap, then set it aside.

2. Break the torque on the caliper banjo bolt with the socket and ratchet, then remove it and the crush-washers from the caliper. Place the fitting into a catch pan, and actuate the brake lever to evacuate all the fluid from the system. Discard the used crush-washers. Inspect the fitting and the banjo bolt for cracks.

3. Break the torque on the master cylinder banjo bolt, then remove it and the crush-washers from the master cylinder. Inspect the fitting and the banjo bolt for cracks. Replace the banjo bolts if they are cracked. Replace the entire brake line if either fitting is cracked.

4. Slip a crush-washer onto the master cylinder banjo bolt. Insert the banjo bolt into the fitting and slip another crush-washer onto the banjo bolt, sandwiching the fitting. Thread the banjo bolt into the master cylinder and torque to factory specifications for your year, make and model of bike. Repeat this process for the caliper fitting and banjo bolt.

5. Fill the master cylinder reservoir with fresh DOT 5 brake fluid. Bleed the brake system according to your bike's manufacturer factory recommendations. Wipe all traces of brake fluid from the fittings. Pump up the brake system firmly, and hold the pressure at the lever. Observe the fittings and check for leaks. Fill the reservoir to the "Full Cold" mark, then install the reservoir cap and cap screws with the screwdriver.

Tips & Warnings

• Cracked fittings or leaks between the brake line and the fitting collar indicate a ruined line. These fittings are swaged on at a factory and cannot be repaired by any means. Never attempt to re-use such lines, as this will create an unsafe condition.

• Do not agitate DOT 5 brake fluid. The fluid will hold small air bubbles in suspension and create spongy brakes. Allow dropped or shaken bottles to rest for 24 hours before adding the fluid to the system.