Blown clutch slave seal (I think)

[Gearbox Paul]

Rode the bike yesterday and noticed the clutch would only disengage the tranny at the very end of the clutch lever travel, which was something new.  By the time I got home, the clutch would not disengage at all and I had to limp home in second gear.  Clutch lever felt very spongy with little resistance.  I opened the clutch reservoir and the level was low.  Refilled and bled the system with a vacuum pump multiple times - unable to generate any resistance at the clutch lever or to get rid of air in the system.  I then took the slave cylinder off and found brake fluid on the engine side of the cylinder.  That should be dry correct?  If there is brake fluid there, I assume it is leaking past the slave cylinder seal.  In my little brain, that would explain the loss of brake fluid and inability to bleed the system.    I believe I need to replace the slave cylinder seal and dust boot, clean up any rust on the cylinder and housing, reassemble, add fluid, and bleed.  There is a an oil seal on the clutch rod but I didn't see any oil when I took the slave off so I don't think I need to replace that oil seal.   Does my  diagnosis and logic sound right, or am I missing something ?

[Motofun]

spot on...and hose off that leaking brake fluid before it destroys the paint  (probably too late) 

[Waiex191]

I've had poor luck with the stock slave cylinder even when the bike was pretty new.  Seems like every couple of years I'd have to pull it off and apart, clean up the corrosion, and put it back together.  Last time it only lasted a few months and I ended up buying a new Oberon slave cylinder.  So far it's great.  I think you can also get a new slave from RPM if the corrosion inside the cylinder is too bad.
https://www.oberon-performance.co.uk/yamaha/yamaha-clutch-slave-cylinder

https://www.rpmracingca.com/proddetail.asp?prod=Clutch%3A5EA-16381-00%3A36y-16381-00
RPM also has a rebuild kit for the slave.
https://www.rpmracingca.com/proddetail.asp?prod=Clutch%3AS%2FK&cat=39

[red]

It would be my choice to replace a bad clutch slave cylinder with a new one, and maybe rebuild the old one when and if time permits. That old thing has probably done enough, so far, and I would not go to any real trouble to "save" it now. Any corrosion or gouging inside the cylinder would be more trouble that it is worth, to me. I would favor a new one especially if it came with an upgrade steel inner lining.
If you favor SpeedBleeders (.com), this would be a good time to add one there. Those folks will know which one you need.

[Waiex191]

It would be my choice to replace a bad clutch slave cylinder with a new one, and maybe rebuild the old one when and if time permits.

I've recently acquired a Bridgeport vertical mill and may try to put a stainless liner in my OEM one like others have done.  As if I'll ever get through my project backlog and actually do that...

[Pat Conlon]

spot on...and hose off that leaking brake fluid before it destroys the paint  (probably too late) 

DOT 5 for me, no need for me to worry!

[racerrad8]

We have you covered, from new Yamaha slave cylinders and slave rebuild kits.

Don't forget to check your clutch lever and busing for wear too. We have those parts as well.

Have a look at this link for that info: https://fjowners.com/index.php?topic=15382.msg155413#msg155413

Randy - RPM