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See also: Revised Clutch Slave Cylinder

By Flange 29Nov2003:  Removed the leaky clutch slave cylinder today. Here's the story.

Remove two Allen bolts - the top one is longer, and there's a long alloy spacer between the slave cylinder & the side of the block which is positioned on the top bolt. The slave cylinder needs some gentle and even leverage to persuade the locating peg to let go.

Applied a little compressed air to blow the piston out, cleaned everything up & inspected the parts.

The bore of the slave cylinder was quite marked with a ring of pitting about 1mm wide, about 10mm from the bottom of the bore. This point seems to coincide with the extremity of the piston's travel. Unfortunately it doesn't show too well on the photo below, but it is what I would consider to be quite severe for a six month old part.

The piston had a patch of light corrosion about 2mm wide, covering about a quarter of the circumference of the piston.

I could find no bad "patches" on the seal, but by comparison with the new seal the original one appeared to be either quite a bit thinner, or had packed down quite severely. In the photo below the original seal is on the left, the new one on the right.

Dressed up the piston with some 1200 wet & dry, and was able to get rid of the corrosion completely.

Dressed up the bore with the same, sufficient to get a uniformly smooth and shiny finish, but the pitting was too deep to take out without enlarging the bore to an unacceptable degree. If the cylinder develops another leak, then it will need replacing.

Lubed everything well with hydraulic fluid, reassembled. The new seal is a much snugger fit than the old. Replaced the assembly, taking care that there was no crud where the alloy spacer sits up against the side of the block. Bled the air out, & the clutch action feels good. Will take it for a road test in the morning.

Why does the seal go ? The inside face of the assembly was quite dirty, I guess from the oily, gritty crud which builds up from the chain, around the front sprocket area. The piston goes in and out, each time picking up more crud and gradually transferring it back onto the seal. If mine does go again, I will ask for a new assembly then turn a groove into the front of the piston and fit an O-ring to keep the crud out.

AndyW:  I know Flange doesn't have the benefit of a Suzi Dealer but for the majority of us we've got two years warranty to fall back on - from what's been described here should a fluid leak result I'd expect the Dealer to take care of it...definately something to keep an eye on though.
Update: several members have had the whole slave cylinder assembly replaced under Warranty.

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