ST1100 clutch engages in last 10% of travel

[PmodelinUS]

The master cylinder rebuild kit is at partzilla for under $30. Its the OEM one.

45530-HN8-006

 

[Bigalone]

I just rebuilt the primary cylinder, as recommended. It was an easy job - the only thing that surprised me was the little metal shield inside the reservoir that covered the compensation port. I knocked it out without noticing and didn't know which way it went back in. But I found photos on this forum.

Sure enough, the compensation port was totally clogged, exactly as this forum said it would be. I cleared it with the wire from inside a twist tie, scrubbed everything with brake fluid and put it back together.

When I initially bled the primary, I couldn't get the fluid to flow until I used my finger to cover the outlet hole on the primary and keep air from getting sucked back in. Once I got the fluid moving I connected the hose, bled it again at the secondary, and everything worked.

The test ride was good but short, so I'll have to do a longer ride to tell me if the fix holds.

Thank you ST1100 owners!

 

[jfheath]

Good result. Glad you got it sorted.

And thanks for letting us know what you discovered. It is really helpful - not only to those who replied, but also to people searching for possible answers in the future.

A good technique for bleeding is to leave the bleed valve closed. Rapid pump the lever a few times and hold the lever in. This builds up air pressure. Keep the lever held back, Open the bleed valve and let the air pressure eject the fluid and air through the bleed tube. Close the bleed valve just before air or fluid has stopped coming out . Release the lever.

Repeat.

At first it feels that you are not making progress, even though you are. This method keeps the ensures that the system is never open at both ends at the same time. It does what your finger was doing, but has the benefit that it compresses the air bubbles ( which helps to dislodge them) and uses the air pressure to eject the fluid / air at the bottom.

The non return bleed tubes are a good investment, but they are less effective when the system is empty.

 

[George]

Over many years, my STs have suffered all the maladies listed in this post. I even replaced the clutch springs on STick which cured a minor slipping condition. Also replaced her secondary clutch valve. Murphy's Law applied to ST1100.