Motorcycle Repair: Front brake hydraulics, brake hydraulics, yamaha v star

Question
Chris,

     I was adjusting my brake lever positioning and loosened the brke line. Of course Now I have no front brakes. I'm sure I need to bleed them. Please explain to me how to bleed my front brakes? I have a 1999 Yamaha V-Star Classic 650.

Answer
Hi Don
Bleeding a brake system is both a simple and complex proceedure.  It's very similar to bleeding the brakes on a car.

The basic proceedure is as follows:

1)  Put the bike on the centerstand and remove the cover (cap) of the master cylinder.

2) Fill the clean container with some brake fluid, but don't use it all. Attatch the bleeder hose to the bleeder valve (it's a nub with a hexagonal base to it at the top of the brake itself).  Put the other end into the container that you just put brake fluid in.  Open the bleeder screw a bit while pressing down on the brake pedal/lever and close it before you let up on the pedal/lever.  You will probably see bubbles in the line.  Be sure to refill the master cylinder before it get's too low and repeat this process until you no longer get bubbles in the bleeder line.

3) Tighten and close everything up when done.

4) Ride away and have fun.

Some bikes have an additional problem with both the clutch and front brakes, including my own.  The problem stems from the configuration of the master cylinder, which is that the connection to the hydraulic line at the master cylinder creates a pocket that air bubbles like to hide in (this is called a reverse trap) and the method for bleeding that section is a little tricky if you've never done this before.

 Here's the proceedure;

1) Bleed the clutch/brake line like normal.

2) Put a wrench on the banjo fitting and squeeze the lever.


3) (NOTE: Use a box end wrench for this) While holding the clutch/brake lever in, crack loose the fitting and reclose it quickly. Have a rag over the fitting connection that you are working on because it will spit at you as pressure expells the air and a little fluid.
IMPORTANT NOTE: Do not release pressure on the lever till the fitting is tightened back up or you will suck air back into the line.

4) Test the clutch/brake again.  If done correctly, you will have pressure near the beginning of the lever movement rather than at the end.

5) repeat as needed, but should not need more than 2-3 times.

Good luck.
FALCON