Motorcycle Brake Service
As with any other working part of the motorcycle, the brakes require periodic adjustment, cleaning and replacement. I can't possibly overemphasize the importance of good workmanship when servicing motorcycle brakes.
Single and Double Leading Shoe
Adjusting the free travel in a single leading-shoe brake should begin by loosening all the slack in the cable at the hand lever. Take up the slack at the brake-control lever at the wheel. Readjust the hand lever for proper free play at the handlebars. Adjust the rear brake by tightening the nut on the brake rod until pedal free play is correct. Remember to readjust the rear brake after making any chain adjustment or a rear-wheel alignment.
Double leading-shoe brakes have the same adjustment features as a single leading shoe with one addition. There is also a brake-balance bar or connector link between the two cam levers. It is very important that this bar be adjusted so that both brakes contact the drum simultaneously and with the same force. This is accomplished by lengthening or shortening the ends of the rod until both shoes contact the drum at the same time.
The main adjuster on a disc brake system is generally the rotor-caliper positioning adjustment. This is a threaded adjuster that positions the caliper to reduce or increase the amount of "float" it uses before the braking action begins. This adjuster should be positioned to allow about 3/4 inch travel of the hand lever. Check the fluid level in the reservoir that is part of the hand lever assembly. If it is low in fluid, inspect the system for wetness or leaks. Sponginess in the lever or front brake feeling may be caused by air in the disc slave cylinder. This air is removed by "bleeding" or allowing some of the brake fluid to escape along with the air.
To bleed the disc brake slave cylinder, follow this general procedure, although you should always follow your manufacturer's exact instructions:
1. Ensure that the master cylinder is filled with fresh disc brake fluid.
2. Apply light hand lever pressure to the hydraulic brake system.
3. Open the slave cylinder vent valve slightly, allowing the air and some fluid to escape. Use precautionary measures to keep the brake fluid off of the brake disc, brake pads, and painted surfaces of the motorcycle.
4. Close the valve before releasing the hand lever pressure.
5. Repeat this sequence until no air escapes with the brake fluid. Do not allow the master cylinder reservoir to become less than half full.
6. A final filling of the reservoir and wiping down of the bike of stray fluid completes the procedure.
The best repair technique for brakes is simply to replace worn parts with new ones. The most frequently worn parts are the brake shoes and springs. It is a good idea to replace springs along with shoes even though the old springs still function.
Often brake cams are not properly contoured at the factory, but you can get better braking action by smoothing the rough edges of the cams.
The drum-hub assembly can be reused even if it has been scored or scratched a little, but it should be replaced if it is severely gouged or drastically "out of round." In an extreme emergency, motorcycle hubs can be turned on a lathe, but this practice is not recommended.
Disc brakes are relatively easy to service. After removing the rotor and retaining clips, the old pads can be removed very quickly. You simply slip the old brake pads out and slip new ones in. Be sure to keep grease, brake fluid, and dirt away from the fiber lining of the brake pads. Check carefully and if you detect any leak in the hydraulic system the unit should be honed and the piston seals replaced.
Honing a disc-brake cylinder insures that the new piston seal will have a suitable surface to seal against. This honing should be done only with a special disc-brake hone. Refilling and bleeding will then be necessary.
A small dab of lubrication, such as white grease, should be applied wherever there is metalto- metal movement in the brake system. The cam-shoe area and shoe-to-backing plate area are the most important areas. But don't overdo it - a very thin film of lube is all that's needed.
When any brake part is replaced, make fresh adjustments after you reinstall the assembly on the bike.