Hydraulic motorcycle clutches are great compared to a traditional cable-actuated setup. They have a light pull, you don’t have to adjust them, and they are more consistent feeling than some cable versions. With all that awesomeness comes a little bit of care beyond the lubing and slack adjustment required from a cable setup. This time on MC Garage we talk about changing the fluid in your hydraulic clutch.
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How Does A Hydraulic Motorcycle Clutch Work?
Just like the braking components on a modern motorcycle, a hydraulic clutch uses pressure applied by a lever through a piston in the master cylinder to transfer that force to the slave cylinder. It pushes its piston out (just like on your brake calipers) to actuate the pushrod. That moves the pressure plate, releasing the force holding the fiber and steel plates together, thereby uncoupling the transmission from the crankshaft.
Over time, you may notice that the actuation of the clutch may feel less consistent or notchy. The fluid could get an air bubble trapped somewhere in the line, but also hydraulic fluid will absorb water from the air, which will eventually lead to corrosion. When this happens the fluid becomes murky or discolored. Or it may be the time for a refresh according to your manual. Either way, we are going to change it.
If you’ve ever flushed brake fluid, then you are well equipped to do this. The method is very much the same.
What Do I Need To Flush A Hydraulic Clutch?
To complete this job you’re going to need the proper fluid. Most systems use the same fluid as the brakes: DOT 4, 5, or 5.1. But some use straight mineral oil, usually Magura systems. Once you have your oil, you just need a clear tube, a catch bottle, an 8mm wrench for the bleed nipple, a syringe or another method to suck the fluid out of the reservoir, and whatever tools it may take to remove the cover or cap on the master cylinder reservoir.
How To Bleed The Hydraulic Clutch?
Pop the top on the reservoir, making sure you lay out rags to protect the paint if you have any drips. Check out the rubber diaphragm. Check it over for any tears, pinholes, or cracks. Give it a good wipe-down with a paper towel; rags leave fiber and fuzz. Do not use brake cleaner or contact cleaner on this; those chemicals will make the rubber swell or distort and it won’t seal properly when you install it.
Next, suck the majority of the oil fluid from the reservoir. Then fill it up with the new fluid that you will be pushing through the system to flush out the old. You want to use a new bottle, as hydraulic fluid can absorb water over time, whether that’s in the system on your bike or in the bottle on the shelf. Fresh is best. As we move the old fluid down and out through the lines, you want to make sure the level of the fluid in the reservoir doesn’t drop so low you suck air. Or you’ll be back to square one.
At the slave cylinder, put your wrench over the nipple and attach the clear hose. The tube should reach the bottle of the catch bottle; I like to make a hole in the cap to hold the tube and keep it in place. Having some fluid at the bottom and covering the tube helps to keep air from traveling up and back into the system.
Just like bleeding your brakes, squeeze the lever and then loosen the nipple just enough for the fluid to come out. Do not release the lever until you close the nipple. You won’t have the firm and then soft lever like on a brake system to remind you that you are pushing fluid through the system, so it’s easier to forget to keep the lever in until the bleeder is closed. Repeat the squeeze, crack, close, and release until the fluid runs clean. And keep your eye on that fluid level!
After the fluid is clear, replace the reservoir diaphragm and cap. Clean up. Give the lever a few squeezes, fire up the bike, and check the operation. That’s it!
Find out more: https://www.motorcyclistonline.com/how-to-service-motorcycles-hydraulic-clutch/
Thanks to Maxima Racing Oils
https://www.maximausa.com/
Videography: Ryan Schutlz
Edit: Bert Beltran
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