Brake Bleeding

When you install Yamaha’s Racing Kit Engine Control Unit (ECU), the Automatic Braking System (ABS) or Brake Control (BC), as Yamaha calls it, is no longer a provided function. Which is alright with me! Having the ABS kick in on corner entry was startling and I started to develop a lighter brake lever approach to braking. The opposite of what my rider coach is trying to get me to do.

So, out with the ABS pump, and out with the ABS lines! And installed some steel braided brake lines from Core Moto. The brake lever “feel” on my Yamaha R1 with the ABS installed was just perfect. The lever would build pressure, with just the smallest of movement. This gives it a hard feeling. In my opinion. As a matter of fact, it would start to build brake pressure just BEFORE the audible click on the brake light switch. Meaning, the click represents the point where the brake light turns on. The brake lever feel on my RC51 is soft. It moves quite a bit before you feel the lever build pressure. To remedy this, without success, I have rebuilt the master cylinder, removed the old rubber lines, installed new steel braided brake lines and rebuilt the brake calipers. Then, I thought, maybe there is still some air trapped in the lines? “But I have bled the brake lines on that RC51 thousands of times.” Well, maybe not thousands of times, but you get the point. Some people on the forums say Honda designed the brakes to be that way. Apparently, some people like this soft feeling brake lever. They probably see a hard lever as something that is too touchy.

With the steel braided brake lines installed on my R1 and the brakes bled. The brake lever was starting to build pressure AFTER the audible brake switch, “click.” Damn it! So I proceeded with my usual. Bleed some more, which never makes it any better (the lesson here is, if something isn’t working, don’t keep doing the same thing).

I usually use a pneumatic brake bleeding tool that sucks the brake fluid through the lines. This works quickly for getting a large volume of brake fluid through the lines. Then, I’ll use the classic clear plastic hose attached to the bleed screw and the other end into a plastic bottle. This method works well for firming up the brake lever feel. This is the point that I got to with my R1, where I said, “Damn it!” I was thinking to myself, there must be air bubbles still trapped in there. And then, I started thinking like a smart human being. I remember that someone in the past mentioned that if the brake lever felt soft on your dirt bike just after bleeding it. To unbolt the caliper and force the caliper piston back into the caliper by pushing the caliper against the brake rotor. This method forces a lot of fluid back into the reservoir, and with it, maybe some air bubbles. Which immediately fixed the soft lever feel I had on my 2006 Yamaha YZ450.

As a matter of fact, on a current generation R1, you have to spread the brake pads (which in turn, pushes the caliper pistons back into the caliper) to remove the brake calipers from the wheel. Because there is no room to slide the calipers rearward off the rotor. They hit the inner side of the rim. To spread the pads, you need to remove the brake caliper bolts and turn the calipers at an angle to the brake rotor, left and right. Once the brake pads are spread, you have to rotate the calipers slightly outward and rearward, to get them off the rotor without hitting (scratching) the wheel. This method of spreading the brake pads and forcing the caliper piston back into the calipers, didn’t firm up the brake lever. Damn it!! Again.

Maybe I’ll use the old zip-tie trick?! I learned this one back when I had a 1996 Suzuki GSX-R 750. You zip-tie the brake lever to the handlebar, as if there is a finger forever pulling on the brake lever. Let it sit overnight. You can also try tapping, flicking, or wiggling the brake line to encourage the air bubbles to move up to the reservoir. I used this method on the R1 and a couple of days later I cut the zip-tie off. And bam! The brake lever had that instant firm feeling that I liked so much before removing the ABS lines.

You might be thinking so why don’t you use the other methods to the RC51? Trust me, I have. Maybe it’s time to try an upgraded master cylinder.

If you have any other brake bleeding tips and tricks, let me know: [email protected]

Edited March 30th, 2025.