My Experience with the Hebo Universal Hydraulic Clutch Kit

I recently decided to replace the cable clutch on my XR400 with a hydraulic one, as all the reports suggested it made a significant difference in terms of ease of use and levels of maintenance. There are a few options available, but I decided to try the Hebo Universal Hydraulic Clutch Kit.

This choice was made partly based on cost, but also on the fact that I can be quickly and easily revert back to the cable should I wish to transfer the kit to another bike. In addition, some of the kits required specialist fluid, but the Hebo uses standard DOT4 brake/clutch fluid.

The Hebo kit comes with a large variety of fittings which should enable it be used to replace most cable-operated clutches. The idea is simple; remove the cable and replace it with a hydraulic cylinder at each end with a length of braided hose in between. The slave cylinder effectively pulls a small length of cable to operate the clutch in the same way as the original cable would. This removes the friction (and any ‘stiction’)  between the full-length inner cable and outer sleeve.

Prior to mounting the slave cylinder, it is a pretty simple task to mount the clutch lever and master cylinder. At the same time, route the hose as smoothly as possible towards the proposed mounting point for your slave cylinder. The choice of where to mount the slave cylinder is down to your own personal preference. Some people like to mount the slave cylinder high up on the frame in order to keep it relatively mud-free, but I decided against this for two reasons: 1) Maximum benefit would be obtained by reducing the length of cable to an absolute minimum and keeping the cable run as straight as possible, and 2) the unit comes ready-assembled with a braided hose of a certain length which needs to go somewhere, or be cut and crimped accordingly. I do not have the tools or inclination to modify the hose.

I decided to mount the slave cylinder just in front of the engine, under the header pipes. This enabled me to retain about 1 inch of outer sleeve for the cable which is probably the minimum possible for the XR400, and just allows sufficient flexibility to move the slave cylinder away from the exhausts a little.

In order to make this fit whilst keeping a nice clear run for the clutch hydraulic pipe, it was necessary to turn the pipe fitting around on the slave cylinder, which then required the system to be bled. This is not too difficult, and is best done by connecting a large syringe full of hydraulic fluid (DOT3) to the bleed nipple with the slave cylinder not mounted on the bike, loosen the bleed nipple and slowly ‘inject’ the clean fluid back up through the system to the master cylinder, pushing any air with it. It is necessary to ensure that the master cylinder does not overflow whilst this is happening, so a second syringe is handy for removing the excess from the master cylinder before it spills!

I made a simple mounting bracket from a strip of flat aluminium, which attaches the slave cylinder to one of the frame engine mounting bolts. It does not need to be particularly strong, is this simply locates the cylinder and does not really take any stress. In addition, I fabricated an angled aluminium ‘deflector shield’ (!) which serves 2 purposes: 1) protects the slave cylinder from the worst of the mud/dirt, and 2) acts as a heat-sink to stop the exhaust heat boiling the fluid in the slave cylinder.

Once fitted, my first thought was that the clutch was not properly connected, as the action was so light. However, putting the bike in gear and rocking it with the clutch in showed that it was indeed fully engaging & disengaging.

In use, my clutch action is now extremely light (1 finger would do it) and smooth. Even though the original XR4 cable clutch is not particularly heavy anyway, the difference is huge, and if you are in a slow, technical situation where you are having to feather the clutch, it is a great improvement. There is also no need to fully lube the cable after every ride, as was the case previously!

Overall, I am very pleased with the Hebo Universal Hydraulic Clutch Kit. Although it is not cheap, it makes the bike much easier to ride through the technical bits, and will hopefully reduce maintenance too.

Alex Tooze