General
Master cylinders designed for dual disc (two caliper) operation have an 17.5 mm (11/16 inch) bore.
![](https://motoinstruction.ru/img/harley/2/111324.jpg)
Figure 2-39. Front brake master cylinder: 1. Screw; 2. Sight glass; 3. Cover; 4. Gasket; 5. Master cylinder reservoir; 6. Collar; 7. Steel/rubber washers; 8. Banjo bolt; 9. Brake line; 10. Bushing; 11. Brake hand lever; 12. Retaining ring; 13. Spring retainer; 14. Spring; 15. Primary cup; 16. Piston; 17. O-ring; 18. Wiper; 19. Piston cup; 20. Handlebar clamp; 21. Screw and washer; 22. Pivot pin
Removal and disassembly
1. Open bleeder nipple caps on front brake calipers. Install clear plastic tubing over each caliper bleeder valve, while placing free ends in a suitable container. Open bleeder valves about 1/2-turn. Pump brake hand lever to drain brake fluid from reservoir. Close bleeder valve. See 1.9 Bleeding brakes.
Caution! Damaged banjo bolt surfaces will leak when reassembled. Prevent damage to seating surfaces by carefully removing brake line components.
2. See Figure 2-39. Remove banjo bolt (8) and two steel/ rubber washers (7) to disconnect fitting of hydraulic brake line from front brake master cylinder. Discard washers.
Caution! Do not remove the master cylinder assembly without first placing a 4 mm (5/32 inch) thick cardboard insert between the brake lever and lever bracket. Removal without the insert may result in damage to the rubber boot and plunger of the front stoplight switch.
3. See Figure 2-40. Place cardboard insert (2) between brake lever and lever bracket.
![](https://motoinstruction.ru/img/harley/2/111325.jpg)
Figure 2-40. Front brake master cylinder and reservoir: 1. Groove; 2. 4 mm (5/32 in.) thick cardboard insert
4. See Figure 2-39. Remove screw and washer (21) to detach handlebar clamp (20) from master cylinder reservoir (5).
Warning! Always wear proper eye protection when removing retaining rings. Use the correct retaining ring pliers. Verify that the tips of the pliers are not damaged or excessively worn. Slippage could propel the ring with force which could cause death or serious injury.
5. Remove retaining ring (12) from pivot pin (22) groove.
6. Remove pivot pin (22) and brake hand lever (11).
7. Carefully remove wiper (18) with pick or similar tool.
8. Remove piston cap (19).
9. Remove piston (16) with o-ring (17) and primary cup (15).
10. Remove spring (14).
Caution! To prevent dirt and other contaminants from entering the master cylinder reservoir, thoroughly clean the cover before removal.
11. Remove both screws (1), cover (3) and the cover gasket (4).
Cleaning and inspection
1. Always assemble master cylinder using new parts from repair kit.
Warning! Clean brake system components using denatured alcohol. Do not use mineral-base cleaning solvents, such as gasoline or paint thinner. Use of mineral-base solvents causes deterioration of rubber parts that continues after assembly. This may result in improper brake operation which could result in death or serious injury.
2. Clean all parts with denatured alcohol or DOT 5 SILICONE BRAKE FLUID. Do not contaminate with mineral oil or other solvents. Wipe dry with a clean, lint free cloth.
Warning! Low pressure compressed air can blow debris into your face and eyes. Always wear eye protection and a face shield when using pressurized air. Failure to take adequate safety precautions could result in death or serious injury.
3. Blow out drilled passages and bore with a clean air supply. Do not use a wire or similar instrument to clean drilled passages in bottom of reservoir.
4. Carefully inspect all parts for wear or damage and replace as necessary.
5. Inspect piston bore in master cylinder housing for scoring, pitting or corrosion. Replace housing if any of these conditions are found.
6. Inspect outlet port that mates with brake line fitting. If any scratches, dents or other damage is found on this critical sealing surface, replace housing.
7. Inspect cover, sight glass and gasket for cuts, tears or general deterioration. If gasket and/or sight glass replacement is necessary, proceed as follows:
- a. From inboard side, push sight glass toward top of cover until free.
- b. Pull rubber gasket from cover.
- c. Fit nipple of new gasket into hole of cover aligning gasket and cover thru holes.
- d. From bottom of gasket, push flat end of sight glass through nipple until top of glass is flush with top of gasket. Verify that glass is square in bore. If lubrication is necessary, use clean brake fluid.
Assembly
To rebuild front brake master cylinder, use the components found in the SERVICE PARTS KIT No. 45072-96C.
1. See Figure 2-39. Fit o-ring (17) into groove at front of piston (16).
2. Fit primary cup (15) over lip at back of piston (16) so that closed side (smaller OD) contacts shoulder.
3. Coat piston bore of housing with special lubricant supplied in the service parts kit. Also apply the lubricant to OD of installed o-ring (17) and primary cup (15).
4. Clip spring retainer (13) onto end of spring and insert spring (14) into master cylinder bore so that spring retainer snaps into the recess at bottom.
5. Slide piston (16) over spring.
6. Fit wiper (18) over piston cup (19) so that the flat side of wiper contacts cup shoulder.
7. Fit piston cup (19) over piston (16).
8. Press down on wiper (18) until it contacts counterbore. Larger OD of wiper must be completely seated in groove on outlet side of piston bore.
9. Install cover (3) with gasket (4) on master cylinder reservoir. Install two screws (1) to fasten the cover to reservoir, but do not tighten at this time.
10. Align hole in brake hand lever (11) with hole in master cylinder reservoir (5). From top of assembly, slide pivot pin (22) through reservoir (5) and hand lever (11).
Warning! Always wear proper eye protection when installing retaining rings. Use the correct retaining ring pliers. Verify that the tips of the pliers are not damaged or excessively worn. Slippage could propel the ring with force which could cause death or serious injury.
11. Install retaining ring (12) in pivot pin groove. Verify that retaining ring is completely seated in groove.
Installation
Caution! See Figure 2-40. Do not install the master cylinder assembly without first placing the 4 mm (5/32 in.) thick cardboard insert (or cable strap eyelet) between the brake lever and lever bracket. Installation without the insert may result in damage to the rubber boot and plunger of the front stoplight switch.
1. See Figure 2-41. Position brake lever/master cylinder assembly inboard of switch housing assembly engaging tab (2) on lower switch housing (1) in groove (3) at top of brake lever bracket (4).
![](https://motoinstruction.ru/img/harley/2/111326.jpg)
Figure 2-41. Master cylinder and brake lever bracket to handlebar switch housing: 1. Lower switch housing assembly; 2. Tab; 3. Groove; 4. Brake lever bracket
2. Align holes in handlebar clamp with those in master cylinder housing and start both screws with flat washers. Position for rider posture. Beginning with top screw, tighten to 38-72Nm (28-53 ft-lbs).
Caution! To avoid leakage, verify that the steel/rubber washers, banjo bolt, brake line fitting and master cylinder bore are completely clean.
3. Lubricate new steel/rubber washers with DOT 5 SILICONE BRAKE FLUID. Position new steel/rubber washers on each side of hydraulic brake line fitting. Insert bolt through washers and fitting. Thread banjo bolt into master cylinder housing and tighten to 23-31 Nm (17-22 ft-lbs).
4. Install length of clear plastic tubing over caliper bleeder valve, if removed. Place free end of tube in a clean container.
5. Stand the motorcycle upright so that master cylinder is level. Remove master cylinder cover.
Caution! Direct contact of DOT 5 brake fluid with eyes may cause eye irritation, swelling, and redness. Avoid eye contact. In case of eye contact flush with large amounts of water and get medical attention. Swallowing large amounts of DOT 5 brake fluid may cause digestive discomfort. If swallowed, obtain medical attention. Use in well ventilated area. KEEP OUT OF REACH OF CHILDREN.
6. Add DOT 5 SILICONE BRAKE FLUID to master cylinder reservoir until fluid level is 1/8 inch (3.2 mm) from top. Do not reuse old brake fluid. Use only DOT 5 SILICONE BRAKE FLUID from a sealed container.
Warning! Whenever the brake line is reconnected, BEFORE moving motorcycle, you must pump brake fluid until the pistons push the pads against the brake disc. If you don’t pump fluid pressure up again, the brakes will not be available to stop the motorcycle which could result in death or serious injury.
7. Bleed brake system. See 1.9 Bleeding brakes.
Warning! A plugged or covered relief port can cause brake drag or lockup, which may result in loss of vehicle control which could result in death or serious injury.
8. Verify operation of master cylinder relief port. Actuate brake hand lever with cover removed. A slight spurt of fluid will break the surface if all internal components are working properly.
9. Install gasket and cover on master cylinder. Tighten cover screws to 0.7-0.9 Nm (6-8 in-lbs).
Warning! After completing repairs or bleeding the system, always test motorcycle brakes at low speed. If brakes are not operating properly or braking efficiency is poor, testing at high speeds could result in death or serious injury.
10. Test brake system.
- a. Turn ignition switch ON. Pump brake hand lever to verify operation of brake lamp.
- b. Test ride motorcycle. If the brakes feel spongy, bleed the system again. See 1.9 Bleeding brakes.
Note. A sight glass enables the rider to visually check the brake fluid level without removing the master cylinder cover. When the reservoir is full, the sight glass is dark. As the fluid level drops, the glass lightens up to indicate this condition to the rider.