How to Bleed the Brakes on a 1979 Kawasaki KZ1300A
Shop parts for a 1979 Kawasaki KZ1300A Motorcycle.
The KZ1300A carries a lot of mass and a lot of engine, and the only thing that scrubs off speed is its hydraulic disc brake system. On this machine the front brake is a handlebar master cylinder feeding a pair of calipers, and the rear is a pedal-operated master cylinder feeding its own caliper. There is no ABS module and no linked-brake plumbing to work around, so what you have is two independent hydraulic circuits, each bled on its own. That simplicity is good news for a home mechanic, but it does not make the work any less safety-critical. Air anywhere in either circuit turns a firm, predictable brake into a soft, vague one.
Signs That the System Is Due for a Bleed
The most obvious clue is feel. A lever that squashes toward the grip, or a pedal with a long, spongy travel before anything happens, means compressible air is sharing space with the fluid. A lever that used to bite early and now bites close to the grip is telling you the same thing. Pull the reservoir cap and look at the fluid: fresh brake fluid is clear and pale, while fluid that has been in service for years turns dark, cloudy, or tea-colored, and may carry sediment at the bottom of the reservoir.
Brake fluid is hygroscopic, meaning it pulls moisture out of the air over time. That moisture lowers the fluid’s boiling point, and under hard, repeated braking on a heavy bike like the KZ1300A, boiling fluid creates vapor — which behaves exactly like air in the line and can make the lever go long or to the bar. Many riders therefore refresh the fluid on a routine interval even when nothing feels wrong. Bleeding is also mandatory after any work that opened the system: new brake lines, a caliper rebuild, a master cylinder service, or a line that was cracked loose.
Tools and Supplies to Have Ready
- Fresh brake fluid in the type printed on the master cylinder reservoir cap, from a sealed container — once a container is opened it starts absorbing moisture, so old partial bottles are a poor choice
- A box-end wrench that fits the bleeder valve snugly; a box-end grips better than an open-end and is less likely to round the hex
- A length of clear tubing that fits tightly over the bleeder nipple
- A small catch bottle to hang the tubing into
- Rags or shop towels, plus a syringe or turkey baster for lifting old fluid out of the reservoir
- The correct driver for the reservoir cap screws
- Optional: a one-way check-valve bleeder or a vacuum bleeder, both of which make a one-person job easier
Setting Up Before You Open Anything
Get the bike upright and stable on a stand so the reservoirs sit level and you are not fighting gravity. Turn the handlebars until the front reservoir is horizontal, then wipe the cap and surrounding area clean so grit does not fall in when the cap comes off. Drape rags over the tank, the fairing or side panels, the instruments, and anything painted near the master cylinders. Brake fluid attacks paint and many plastics on contact, so treat every drip as urgent: wipe it immediately and flush the area with water rather than letting it sit.
Bleeding the Front Circuit
- Remove the reservoir cap and diaphragm, then use the syringe to draw most of the old fluid out. Leave a little in the bottom so you do not push air into the line.
- Top the reservoir up with fresh fluid from the sealed container, stopping below the full mark to leave room for the diaphragm.
- Push the clear tubing onto one front caliper’s bleeder valve and route the other end into the catch bottle, with the tube end submerged in a splash of fluid.
- Squeeze the lever slowly and hold it against its stop.
- Open the bleeder about a quarter turn. Fluid and any trapped air will travel down the tube, and the lever will sink toward the grip.
- Close the bleeder fully before you release the lever. Releasing with the bleeder open draws air back in through the nipple.
- Let the lever return slowly, then repeat the squeeze–open–close–release cycle.
- Check the reservoir every few cycles and top it off. If it ever runs dry, air enters the master cylinder and you are starting over.
- Keep going until the fluid arriving in the tube is clean and free of bubbles, then snug the bleeder.
- Move to the second front caliper and repeat the whole sequence. As a general practice, start with the caliper farthest from the master cylinder and work toward the closest.
Bleeding the Rear Circuit
- Locate the rear master cylinder reservoir, level the bike, and clean around the cap before opening it.
- Draw out the old fluid with the syringe and refill with fresh fluid.
- Fit the clear tubing over the rear caliper bleeder and lead it into the catch bottle.
- Press and hold the pedal, crack the bleeder a quarter turn, then close it before the pedal returns.
- Repeat, topping the reservoir as you go, until the fluid runs clean and bubble-free and the pedal builds a firm, short travel.
Finishing the Job
Tighten each bleeder snugly with the box-end wrench — firm enough to seal, never so tight that you crush the seat or distort the caliper. Bring the reservoir up to the level marking, reinstall the diaphragm and cap, and wipe down every surface you touched. Then inspect the bleeder nipples and the banjo fittings at the calipers and master cylinders for weeping; a dry paper towel wiped across a joint will show a leak immediately.
Testing Before You Ride
With the bike still stationary, pull the front lever and press the rear pedal. Both should feel firm and consistent, and neither should creep slowly toward the grip or the floor under steady pressure. Spin each wheel by hand to confirm the brakes are not dragging. Then, in a safe open area at low speed, apply each brake separately and confirm it bites predictably before you ride normally.
When to Stop and Take It to a Shop
If the lever or pedal will not firm up after several full bleeding cycles, or only firms after being pumped repeatedly, air is still trapped somewhere — often in the master cylinder itself, which may need to be bench-bled or rebuilt. Persistent bubbles that never stop, fluid weeping from a master cylinder or caliper, or a brake that fades under use all point to a problem beyond a simple bleed. Hand the bike to a professional rather than riding on a brake you do not trust.
Related Shopping Categories
Shop Brake Fluid for a 1979 Kawasaki KZ1300A Motorcycle.
Shop Brake Lines for a 1979 Kawasaki KZ1300A Motorcycle.
Shop Brake Pads for a 1979 Kawasaki KZ1300A Motorcycle.
Shop Stands for a 1979 Kawasaki KZ1300A Motorcycle.
Shop Brake Tools for a 1979 Kawasaki KZ1300A 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.
