Bleeding the Brakes on a 1979 Honda CB750L
Shop parts for a 1979 Honda CB750L Motorcycle.Why and When This Service Matters
The 1979 Honda CB750L uses hydraulic disc brakes at both ends, so the front lever and the rear pedal each push fluid through a closed system to apply the calipers. Over time, brake fluid absorbs moisture from the air. That moisture lowers the fluid’s boiling point, and under hard or repeated braking it can turn to vapor, giving you a soft lever or pedal and reduced stopping power. Even if the bike feels fine, many riders refresh the fluid on a regular interval as preventive maintenance.
You should plan to bleed the brakes if the front lever feels spongy or pulls closer to the grip than it used to, if the rear pedal feels soft or travels farther than normal, if the fluid in either reservoir looks dark or cloudy, or after any work that opened the hydraulic system—new brake lines, caliper service, or master cylinder work. A lever that slowly sinks under steady pressure is another sign that air or moisture is in the system.
Tools and Supplies to Gather
Before you start, collect everything so you are not searching for a tool with the reservoir open. You will need fresh brake fluid of the type marked on the master cylinder reservoir cap, from a sealed container. Do not substitute a different fluid type. You also need a box-end wrench that fits the bleeder valve snugly, a length of clear tubing that fits tightly over the bleeder, and a catch bottle to hold the old fluid. Rags or shop towels are essential because most brake fluids damage paint and plastic on contact. A syringe or turkey baster helps remove old fluid from the reservoir, and you will need a screwdriver or driver that fits the reservoir cap screws.
- Fresh brake fluid matching the reservoir cap marking, from a sealed container
- Box-end wrench sized to fit the bleeder valve
- Clear tubing that fits snugly over the bleeder
- Catch bottle for old fluid
- Rags or shop towels
- Syringe or turkey baster
- Screwdriver for the reservoir cap
- Optional: one-way check-valve bleeder or vacuum bleeder for one-person work
Preparing the Bike and Protecting Surfaces
Support the CB750L securely upright on a stand so it cannot tip while you work. For the front brake, turn the handlebars so the front master cylinder reservoir sits level before you open it. Cover the painted surfaces, the plastic bodywork, the instrument area, and any nearby wiring with rags. Brake fluid attacks paint and many plastics, so wipe up any spill immediately and rinse the area with water if fluid reaches a painted or plastic surface.
Work in a well-ventilated area and keep the reservoir cap and diaphragm clean. Do not let the reservoir run dry at any point during the procedure; if it does, air will be drawn into the system and you will have to start over. Keep the fresh fluid container capped when you are not pouring from it.
Step-by-Step Bleeding Procedure
The CB750L has a hydraulic front brake and a hydraulic rear brake, so bleed each system separately. Start with the front, then repeat the same sequence for the rear. If your bike has two front calipers, bleed each caliper one at a time. As a general practice, begin with the caliper farthest from the master cylinder in terms of hydraulic path, then move to the closer one.
- Open the reservoir cap and remove the diaphragm. Use the syringe or turkey baster to remove most of the old fluid from the reservoir, but leave enough to cover the bottom so you do not introduce air.
- Refill the reservoir with fresh fluid from the sealed container, taking care not to spill any on painted or plastic surfaces.
- Attach the clear tubing to the bleeder valve on the caliper. Route the other end into the catch bottle so you can see the fluid as it comes out.
- Squeeze and hold the front lever, or press and hold the rear pedal, to build pressure. Keep it held.
- Open the bleeder valve about a quarter turn with the box-end wrench. Fluid and air will flow through the tubing. Watch the tube for bubbles.
- Close the bleeder valve before you release the lever or pedal. Releasing first will draw air back into the system.
- Repeat the squeeze-hold-open-close-release cycle until fresh, clean fluid comes through the tube with no bubbles. Check the reservoir level often and top it off with fresh fluid so it never runs low enough to draw air.
- If your bike has two front calipers, repeat the process on the second caliper after finishing the first.
- For the rear brake, follow the same sequence using the rear pedal and the rear caliper bleeder. Keep the rear reservoir topped off throughout.
Finishing Up and Checking Your Work
When clean, bubble-free fluid is flowing and the lever or pedal feels firm, close the bleeder valve snugly with the box-end wrench. Do not overtighten it; you want it tight enough to seal, not so tight that you damage the valve or caliper. Fill the reservoir to the correct level marking, reinstall the diaphragm and cap, and wipe away any spilled fluid. Check for leaks at the bleeder valve and at the banjo fittings on the master cylinder and caliper.
Before riding, test the brakes. The front lever and rear pedal should feel firm and consistent, not spongy, and they should not slowly sink under steady pressure. Spin each wheel to confirm the brakes are not dragging. Then test the brakes at low speed in a safe area before riding normally.
Troubleshooting and When to See a Shop
If the lever or pedal will not firm up after several bleeding attempts, if it firms up only after pumping, or if you keep seeing air bubbles, stop and reassess. Persistent air often means a loose fitting, a worn master cylinder seal, or a bleeder that is not sealing. Fluid leaking from the master cylinder or caliper also calls for inspection and repair before you ride. Because the 1979 CB750L does not have ABS or linked brakes, a standard bleed at the caliper is the correct approach, but any hydraulic system that will not hold pressure should be checked by a qualified technician.
Related Shopping Categories
Shop Brake Fluid for a 1979 Honda CB750L Motorcycle.
Shop Brake Lines for a 1979 Honda CB750L Motorcycle.
Shop Brake Pads for a 1979 Honda CB750L Motorcycle.
Shop Stands for a 1979 Honda CB750L Motorcycle.
Shop Brake Tools for a 1979 Honda CB750L Motorcycle.
Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.
