Fluid

In theory, bleeding brakes is simply a matter of bleeding the air out of the system so there’s nothing but liquid brake fluid in the system. This is important because a fluid can’t be compressed to a smaller volume, so any and all pressure created by the piston in the master cylinder is delivered to the piston(s) in the caliper. Unlike liquids, gasses (like air) can be compressed to a smaller volume. Thus any air left in the lines or caliper after bleeding will be compressed when you activate the lever or pedal, resulting in a mushy feeling lever and piss-poor brake performance.

Brakes

Bleeding brakes on your Chevy is often easier than on a motorcycle because the master cylinder is bigger and moves a much larger volume of fluid with each stroke. Typically, you get a friend to pump the pedal two or three times and hold it down while you open the bleeder valve. With pressure on the system you open the valve, a frothy mixture of air and fluid spits out all over your face, and then you close the valve. With the bleeder closed, your helper allows the pedal to come up and then the process is repeated again. Bleeding goes on until nothing but pure, clean brake fluid exits the bleeder each time it’s opened.

You can bleed the brakes on that motorcycle using this time-honored process outlined above. Most experienced builders fill the master cylinder reservoir and then do a series of short strokes, which essentially bleeds the master cylinder. If you try bleeding in this fashion, you will see a series of small bubbles come up into the reservoir with each stroke. Eventually the short strokes produce no additional bubbles. Now you can use the full travel of the lever, pumping it two or three times, and then open the bleeder just as you would on the Chevy. Just remember not to release the lever until the bleeder is closed or you pull air back into the system. Continue stroking until the lever is hard.

If repeated attempts at bleeding don’t result in a hard lever, you have a number of options. You might try to use an EZ Bleeder type of tool. In this scenario, you force fluid in at the bleeder with a fluid-filled syringe until all the air is forced out of the system and pure fluid fills the master cylinder reservoir.

If you have trouble getting a solid-feeling lever don’t feel like the Lone Ranger. Though simple in concept, bleeding bike brakes often turns out to be more hassle than you originally bargained for. Many shops have pressure bleeders that make the job easier, so the next option is to ask for help. Run the bike down to the local shop and ask their assistance in getting the last of the air out of those brake lines.

Brake 2

When it comes to bleeding brakes, motorcycles have a few unique problems. One is the small master cylinder piston, which means it can take a long time to push a bubble of air down the line and out the bleeder. Some handle bars position the master cylinder so the outlet is higher than the lever end, which means a bubble can become “lodged” at the outlet end. The solution is to somehow change the angle of the master cylinder (or take it off the bars) during the bleeding operation.

And sometimes the bleeder valve ends up at the bottom of the caliper, in which case you may have to take the caliper off the mount, put something between the pads and hold it “upside down” while the air is purged from the system.

Just be sure to do it ‘till the lever is good and solid, settle for nothing less than great brake performance, and (with pressure on the lever) check for leaks at all the fittings and connections.