Good stuff.I have a rebuild kit and a boot coming, as well as the balance of the CSC parts to replace.
When you get the rebuild kit - a little silicone grease or red rubber grease around the parts that are covered by the boot is a good idea. Done use 'normal' grease with a petroleum/minera oil base. It makes the rubber boot swell dramatically and it stops sealing. Double check the orientation of the plunger before fitting the boot.
I don't know exactly how the boot is retained in the clutch master cylinder. I did the clutch service kit on my 1100 27 years ago and I don't remember it being an issue. But it didn't seem to lock into place - which tells me that I didn't do it correctly.
You need a tool in order to fit the rubber boot properly. The boot look a bit like a top hat with a brim. The boot has a circular spring - like one of those cheap key rings - inside the brim of the top hat. That needs to be given a firm push until it clicks into place. So something round that will press on the brim and which will also fit inside the bore. For the SMC, I found a socket from my toolkit that was exaclty the correct size. You may be able to manage it with three rounded lollipop sticks (and three hands). Dont be tempted to use small screwdrivers - they will pierce the rubber boot.
The image below is a photo of the SMC from an ST1300. I only show it becasue it is the only time I have ever seen a real cross section of the bore of a master cylinder.
The SMC has been sawn in half down the bore, and the piston service kit and the boot has been put in place for this photo.
It is likely (but I do not know) that the rubber boot in the clutch master cylinder is seated firmly using the same technique as it is in the SMC. But if I tell you about the SMC, then you will be able to tell whether or not the same thing applies. I believe that it does - but that isn't the same as knowing for sure.
Note the rubber boot and the brim of the top hat. When you first put it in, it meets up with the angled step and it won't go any further. But slip a tube down over the boot so that it can press against the brim - the slope of that angled step and the pressure from your tube 'tool' causes the key ring spring inside the boot tocompress and the brim suddenly moved further down the bore. It feels like a definite click as it locks in place. Thereafter the spring pressure on the side of the narrowerebore is enought to keep the boot in place. The action of the clutch lever never tugs on it.
Forget the bit in the image below - labelled 'Drain Hole'- Thats the SMC - the clutch master cylinder doesnb't need on - water on the outside will fall out easily.
When you have the clutch master cylinder apart, take a look inside the bore - see if that narrowing of the bore and the angles step is there. If it is then all of the above is relevant.
If there is nothing there then maybe a groove ?
Someone else will chime in if they have more accurate information. But I do know that it doesn't just rest in place. You will know that when you remove the old one. It takes a bit of a tug.
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