Anyone who's recently installed some braided steel brake lines, new calipers, or a whole new brake system knows what a pain it can be to bleed all the air out of the system. Even with a practiced hand, it can often take 10 minutes or more of constant compressing the brake lever/opening the bleeder valve/releasing the brake lever to begin getting enough brake fluid into the system to get some resistance at the lever, and then you have to start the process of bleeding the air out of the high points in the system (loosening the master cylinder banjo bolt, etc.). It's an elongated job that can tax even the most patient mechanic or do-it-yourselfer.
There are many vacuum brake bleeder kits out on the market that work on the principle of pulling all the air out of the system through the caliper bleed screw (and thus displacing that air with brake fluid). An issue with vacuum bleeders is that they pull the air bubbles downward, the opposite direction that they naturally want to go. And if you have an ABS system, it can be a complicated task, as some of the valves can catch air bubbles when attempting to force them down to the calipers.
Enter the Phoenix Systems brake bleeder that works using the opposite principle: reverse fluid injection, which actually forces the air bubbles out by injecting brake fluid at the caliper bleed screw and forcing it upward through the master cylinder at the top. By injecting the fluid at the bleed screw, you not only push the air bubbles in the direction they want to go, but you can also flush brake systems easier. Although intended for automotive applications, we were given a Phoenix MaxPro brake bleeder kit to try out when installing some brake lines on our Yamaha R1.
The MaxPro bleeder kit's main components (there are numerous other pieces used for various other brake fluid maintenance tasks) consist of a metal injector gun, all the requisite plastic tubing lines, numerous adaptors to fit nearly any bleed screw, and a plastic brake fluid reservoir that the gun draws from. Getting started involves priming the gun with brake fluid so that it doesn't inject air into the system; hooking up all the lines is easy, as each uses leak-free cam-lock-style male/female fittings. Priming the gun took all of three pulls on the lever, as the setup moves a lot of fluid (an added benefit is the gun can also be used as a vacuum pump).
Hooking up the gun to the bleed screw required the correct size adapter, which was fairly easy with the numerous adapters in the kit. The brake master cylinder fluid reservoir needs to be almost empty, as the reverse injection method will force fluid up into it as the air gets displaced. Then it's just a matter of pumping the gun until no more bubbles appear in the master cylinder reservoir and the brake lever becomes firm.
Unfortunately, it wasn't all that easy. For some reason, there was a bit of resistance when pumping fluid into the calipers; the DVD supplied with the kit portrayed pumping to be fairly easy. Because the kit is intended for automobile brake systems that are much higher volume and more elaborate than a comparatively simple motorcycle brake system, the gun moves quite a bit of brake fluid with every stroke. Even with empty brake lines and partially drained calipers, it only took about three pulls before fluid was already filling the brake reservoir-so that part was quick. But that resistance we encountered was surely the cause of our main problem: brake fluid seeping out of the bleed screw threads when pumping fluid through them. We didn't loosen the bleed screws that much, so we thought that perhaps we needed to unscrew them a bit more to release the pressure; but opening them up didn't solve the problem, and there was still a lot of seepage that required rags to keep the fluid leak contained and some cleanup with contact cleaner afterward.
After pumping fluid into both calipers, we were still getting some sponginess in the lever, which turned out to be air trapped in the area where the lines meet the master cylinder banjo bolt. Once we bled out the air from that area, the brake lever instantly firmed up.
The MaxPro kit that we used retails for $369.99, which is a bit pricey-but this version was surely overkill for a job like this. However, Phoenix has a less expensive plastic gun setup with the bare essential components for $79.99.