How to Rebuild a Front Brake Master Cylinder on a 2002 Yamaha Midnight Venture

The 2002 Royal Star Midnight Venture was Yamaha's flagship touring-class cruiser motorcycle. The Midnight Venture's front wheel was equipped with a twin-disc hydraulic brake system that provided enough power to bring the 869-pound motorcycle to a complete stop. However, the hydraulic master cylinder that powers both front brake calipers can be affected by wear, reducing the inner piston's ability to compress the hydraulic brake fluid. This ultimately reduces the motorcycle's ability to stop. The piston and all necessary parts are available as a complete kit from Yamaha, easing the process of rebuilding the master cylinder.

Things You'll Need

• Service stand
• Two, 3-foot long clear plastic hoses
• Plastic container
• 8 mm open-end wrench
• Phillips screwdriver
• 14 mm open-end wrench
• Shop towels
• 10 mm box-end wrench
• Flat screwdriver
• 5 mm Allen wrench
• Internal snap ring pliers
• Air compressor
• DOT 4 brake fluid
• Oil seal
• Master cylinder piston
• piston cup
• Dust cap
• Circlip plers
• Spring
• Torque wrench
• Reservoir diaphragm

Instructions

1. Mount the motorcycle on a service stand to hold it in a vertical position.

2. Remove the dust cap from the bleed valves on the top of both front brake calipers. Push a 3-foot length of clear plastic hose over both valves, then place the free ends of the hoses into a plastic container. Turn the bleed valves counterclockwise a quarter of a turn, using an 8 mm open-end wrench.

3. Remove the lid and diaphragm from the front brake master cylinder on the right handlebar, using a Phillips screwdriver. Pump the front brake lever until brake fluid no longer fills the hoses attached to the brake calipers. Turn the bleed valves counterclockwise to close both valves. Do not remove the hoses at this time.

4. Loosen the right rearview mirror lock nut, using a 14 mm open-end wrench. Unscrew the mirror from the front master cylinder by hand.

5. Wrap a shop towel around the brake hose bolt on the end of the front master cylinder then unscrew the bolt, using a 14 mm open-end wrench. Pull the brake hose away from the master cylinder and wrap the hose fitting tightly with the towel. Wipe the end of the master cylinder with a separate shop towel

6. Remove the brake lever pivot nut from the bottom of the front master cylinder, using a 10 mm box-end wrench. Unscrew the lever pivot bolt, using a flat screwdriver, then pull the brake lever away. Unscrew the front brake switch from the bottom of the master cylinder, using a Phillips screwdriver. Pull the bolt covers out of the master cylinder bracket bolts, then unscrew the bolt, using a 5 mm Allen wrench. Pull the master cylinder away from the handlebar.

7. Remove the rubber dust cap from the master cylinder piston, the portion of the master cylinder that the brake lever presses against. Remove the piston circlip, using an internal snap ring pliers. Pull the oil seal, piston, piston cup and spring out of the master cylinder.

8. Check the master cylinder bore, the hole that houses the piston, for scratches or pitting. Replace the master cylinder if the bore walls are damaged in any way. Blow compressed air through the master cylinder to remove any dirt or obstructions. Coat the master cylinder bore with DOT 4 brake fluid.

9. Coat the new piston, oil seal, piston cup and spring with fresh brake fluid. Slide the spring, followed by the piston cup, piston and oil seal into the master cylinder bore. Place a new circlip into the channel cut into the end of the master cylinder bore to secure the piston, using circlip pliers. Push a new dust cap over the end of the piston.

10. Mount the front master cylinder onto the right handlebar, then tighten the master cylinder bracket bolts to 7.2 foot-pounds, using a torque wrench. Mount the front brake switch onto the master cylinder. Place the front brake lever against the master cylinder piston, then push the pivot bolt into place. Screw the pivot nut onto the bottom of the pivot bolt. Mount the brake hose fitting onto the end of the master cylinder, placing a new copper crush washer on both ends of the fitting. Screw the brake hose bolt into place and tighten it to 22 foot-pounds.

11. Fill the front master cylinder fluid reservoir halfway with brake fluid. Pump the brake lever slowly until air bubbles no longer appear in the reservoir. Refill the reservoir with brake fluid.

12. Open the left front brake caliper bleed valve a quarter of a turn, then pull in the front brake lever. Close the valve, then slowly release the brake lever. Repeat until the hose attached to the left front brake caliper is filled with brake fluid. Tighten the bleed valve and remove the hose. Push the rubber cap over the bleed valve.

13. Refill the front master cylinder reservoir with brake fluid. Bleed the right front brake caliper, using the same method as for the left front brake caliper. Pump the brake lever, once both calipers have been bled. The lever should feel progressively tighter as it moves through its range of motion. Rebleed that front brake calipers, starting with the left caliper, if the lever feels soft or can be pulled back until it touches the right hand grip.

14. Refill the front master cylinder reservoir until the fluid level is centered with the sight glass built into the reservoir. Install a new diaphragm into the reservoir, then reattach the reservoir lid.

15. Remove the motorcycle from the service stand and lower it onto its side stand.

Tips & Warnings

• Brake fluid is a caustic solvent that will remove paint and cause serious skin and eye irritation. Cover your motorcycle's fuel tank and front fender with thick towels to protect its painted finish. Wear protective gloves and eyewear while servicing your motorcycle's brake system.

References

• Yamaha XVZ13TFSP Service Manual; Yamaha Motor Corporation