Dirt in clutch hydraulics
 

I have just put my 748 back on the road, and the clutch slave cylinder started to leak. When I put the new seal in I noticed that the fluid and cylinders were dirty, presumably having worked its way through the slave cylinder.

The new seal is working fine, so far, but I notice that despite cleaning and purging the system thoroughly the fluid in the master cylinder resevoir is dirty again. However I was in DKs showroom yesterday and they had several 748/996's in stock, and I noticed that most of them had dirty fluid too!

So the question is the dirt a factor in causing the system to leak, and is dirt ingress normal? Finally is there anything that can be done to reduce it?

I can't answer your question, but I flushed and replaced my fluid 3 weeks ago and it's already going brown again. The slave cyl gaiter was knackered, so it may be letting dirt get in which has been flung off the front sprocket/chain into that area. I'm going to change the piston and the gaiter just as soon as I get an hour or 2 free.

The clever people will be along in a minute to give you a proper answer ;)

They all do that sir!

Doesn't appear to make any difference though so don't worry about it.

One thing to look at is the pressure plate bearing if its knackered the push rod could spin and damage the cylinder seal . 4D

clutch Fluid
 

Thanks for the link Shazaam!, very interesting thread.

In my case the fluid is certainly not the factory stuff, as it is a 1997 bike, and I replaced all the fluids before putting it on the road, and changed it again when I relaced the seal. Looking at the master cylinder resevoir the discolouration is caused by foreign bodies in the fluid which settle on the bottom of the resevoir. The new fluid has been in for about 10 days and 400ish miles. I use DOT4 fluid

The particles could easily be rubber fron the seal or the O ring, or dirt working its way past the seal in the slave cylinder

If it's got the old type rubber pipe this can cause the promlem it's the rubber brakeing down on the inside, change it for a braided hose.