The Brembo clutch slave cylinders fitted to many Ducati and Aprilia motorcycles eat their seals on a regular basis. As I own two of these wonderful devices – I got annoyed at paying Aprilia prices for the parts.
If your clutch fluid reservoir needs to be topped up – then this is probably the article for you.
This is a complete how to guide to replace the seal on this Brembo slave cylinder.
Perhaps you have a different motorcycle with a hydraulic clutch – the component design and its repair will be almost identical.
If you already know how to do this work, you can buy a complete kit of parts from us for a very reasonable sum by clicking here: Brembo Clutch Slave Cylinder Repair Kit.
Alternatively, if you have never done this before – then please read on. It’s a simple job, and anyone who owns tools should be able to do this .
Preparing To Repair Your Leaking Brembo Clutch
Before you begin, we are going to pull the clutch lever in a little way. This seals the master cylinder, reduces fluid loss, reduces mess and makes bleeding easier.
Use a bungee, string, tape or whatever. You want to just depress it You are not trying to pull it fully to actually disengage the clutch. An inch of movement at the lever end or so is normally sufficient.
Tools. Before you start you will need to ensure you have the correct tools and parts for this job. You will need:
Brake fluid and a replacement seal and silicone grease. Some tubing of the right size to fit over the bleed nipple or a bleed kit.
8 and 12mm ring spanners and a 5mm allen key that you can get into the cylinder mounting bolts.
Whatever tools you need to remove whatever fairing parts obscure the slave cylinder on your bike (that’s none on this Tuono).
Removing Your Leaking Brembo Clutch Slave Cylinder
Firstly – Loosen the 12mm bleed bolt (circled in white) securing the fluid line to the cylinder. Just loosen it briefly and then very gently nip it back up. You don’t want it leaking fluid, but you do want it easy to undo when the cylinder is no longer attached to the motorcycle.
Secondly undo the three 5mm hex sockets (circled in red) securing the slave cylinder to the motorcycle.
Once these are removed if the cylinder does not come free from the motorcycle you may have to give it a gentle tap with a soft heavy object, the shaft end of a hammer perhaps.
Now the cylinder is free from the bike, remove the fluid line from the cylinder by undoing fully the bolt we loosened earlier.
Now it’s off – let’s get it clean so we can work on it properly.
Use whatever degreasing agent you normally use.
If you keep a finger over the hole for the bleed bolt, you will keep the inside of the system nice and clean, and free from water and cleaning fluid.
The Brembo Clutch Slave Cylinder is actually two parts, the cylinder and a mount for the motorcycle.
We need to separate the leaking clutch slave cylinder from the mount.
If it doesn’t separate in your hands, use a screwdriver in the drain hole at the bottom of the cylinder, circled in white here.
You should have two clean parts.
The cylinder is on the right.
Repairing Your Leaking Aprilia Clutch Slave Cylinder
Pull the piston out of the middle of the cylinder.
Remove the spring from the end of the piston. It’s just a push fit.
If you are replacing the clutch pushrod seal (you often don’t have to, but we provide it in the repair kit we sell), then pry it out of the cylinder with a small screwdriver as shown.
Work around the seal till it is moving small amounts from all sides and work it out of the cylinder.
Use a very fine screwdriver to CAREFULLY (you don’t want to scratch the piston surface) remove the hydraulic seal from the piston body. Work it round the piston till the seal is removed.
Note that the sealing flange on the seal points inwards, in the direction of the spring. That is where the fluid pushes the piston from.
This makes it far easier to slide the seal onto the piston, and to refit the piston to the cylinder. It also makes it far less likely that you will damage the seal during the refitting processes above.
Once you have lubricated the seal and piston, you can normally wriggle the seal onto the piston with your fingers.
Use a small screwdriver as you did for removal if you cannot do this without tools.
Replacing Your Repaired Ducati Clutch Slave Cylinder
Replace the spring on the back of the piston.
Add a small amount of silicone grease to the inside of the cylinder to aid refitting the piston to it.
Position the piston in the cylinder and advance it down so that the seal is at the entrance to the cylinder.
GENTLY work the seal into the cylinder. You can use your nails or similar to easy the seal in if it needs it. Be careful, don’t use anything sharp here.
Once refitted the piston should sit as shown with the seal inside the cylinder.
Now refit the carrier component to the back of the cylinder.
Take the cylinder to the bike, and refit the fluid pipe with it’s bleed bolt and associated washers. The book says we should replace the washers, but I have never had one leak yet.
Tighten the three hex bolts securing the cylinder to the bike, then tighten the 12mm bleed bolt.
Check that you can undo the 8mm bleed nipple from the top of the bolt and then remove the bungee or similar holding the clutch lever partially depressed.
Bleeding Your Ducati Or Aprilia Clutch
Fit your bleed pipe or bleed kit to the nipple after you have positioned your ring spanner correctly.
Remove the top of the master cylinder reservoir and remove the seal underneath. If your reservoir is part of the master cylinder (not on these bikes) you should rest the lid without the seal in place to stop it spitting brake fluid over your bike.
Bleed as normal, which is for the uninitiated: 1) Open nipple 2) Squeeze lever 3) Close Nipple 4) Release Lever 5) WAIT until fluid level stops going down. It takes TIME for the gentle vacuum in a system with air in it to refill the fluid through the small hole in the master cylinder. Repeat from 1.
Continue doing this until you have no bubbles exiting the bleed nipple and the clutch feels correct when operated normally.
Remember to top the fluid up periodically – you do not want to introduce more air in from the top of the system.
If the system is not taking brake fluid in – the most likely cause is that the adjuster inside the brake lever is set too long. Make sure that the lever can move a small way before it actually touches the piston on the clutch master cylinder. This is easily adjusted after removing the clutch lever.
So. This is a simple job that anyone should be able to do. The correct hydraulic seal must be made of EDPM to withstand the brake fluid. You can buy a complete kit of parts, hydraulic seal, clutch pushrod seal and some silicone grease from here.