Clutch Hydraulics
About Clutch Hydraulics
A hydraulic clutch uses fluid instead of a cable: a master cylinder at the lever pushes fluid down a line to a slave cylinder at the engine, which releases the clutch. Riders shop here for a leaking or sticking cylinder, a lever that has gone soft, a replacement master cylinder or a rebuild kit.
Rebuild kits renew the seals and boots and are the usual fix for a leak or a sticking piston, with master cylinder and slave cylinder kits listed separately. A whole cylinder is the answer when the bore is scored or corroded.
Master cylinders are listed by bore size, such as 11/16 inch, and by style, for example radial, so match the style to your lever and keep the size paired with the system. Slave cylinder kits here are listed for Husqvarna and KTM models, and a clutch actuator is listed for Harley-Davidson years. The fluid type is printed on the reservoir or in the manual, and the system must be bled after any work. A few cable listings also appear in this category, so confirm a part is hydraulic before you order.
Brands here include Covingtons, Braking, Drag Specialties, Barnett and PSR. Pick your machine in the Ride Finder at the top of the page. For bikes with a cable clutch see Clutch Cables, and for the parts the cylinders operate see Clutch Plates & Discs and Additional Clutch Parts, all within Clutch Parts & Kits.
FAQs on hydraulic clutch parts
How do I bleed a hydraulic clutch?
Fill the reservoir with the fluid your manual specifies, fit a clear hose to the bleeder on the slave cylinder, pump the lever and hold it, then open the bleeder briefly and close it before releasing. Repeat until no bubbles appear, keeping the reservoir topped up. Follow your manual's exact sequence.
Is clutch fluid the same as brake fluid?
On many bikes it is, usually DOT brake fluid, but not on all of them. The fluid type is on the reservoir cap or in the owner's manual. Do not mix types, and keep brake fluid off paint, because it can damage the finish.
Should I rebuild or replace a clutch master cylinder?
A rebuild kit is enough when the cylinder leaks or sticks but the bore is smooth. If the bore is pitted, scored or corroded, new seals will not fix it and the cylinder should be replaced. Inspect the bore with the piston out before you decide.
How do I know if the slave cylinder is leaking?
Look for fluid around the slave cylinder or running down the engine case, a reservoir level that keeps dropping, and a lever that goes soft or to the bar. A clutch that will not release can also point to it. Fix the leak, then bleed the system.
Why does my hydraulic clutch lever feel spongy?
Air in the line or worn seals are the usual causes. Air is removed by bleeding, and worn seals by a rebuild kit. If the lever still feels soft after a clean bleed, check the hose and the cylinders for leaks.
