Clutch master or slave? That is the question

kaplang

kaplang

Joined
Apr 21, 2008
Messages
26
Location
Calif
1997 with 64,000 miles
Clutch stopped working. Has air in the line and it won’t bleed. It’s not the hose because I see no sign of leaking and the reservoir was full when I removed the cover but the fluid looks contaminated. I use Lucas dot 3 synthetic oil. I can’t determine if it’s the master or slave. Is their a process I can use. I don’t want to rebuild the wrong one.

This has been going on for a long time. It would pump up if I exercised the clutch lever and would be fine for a long time. Now it won’t and I have absolutely no clutch engagement. Or is that suppose to be disengagement? I get them confused.

Thanks
 
Fear not. Some one will come along here that knows a lot more than me on the ST1100 clutch system. But in the mean time I saw in my manual that Honda Dot 4 brake fluid is recommended. Hope it helps.
 
red one said:
Fear not. Some one will come along here that knows a lot more than me on the ST1100 clutch system. But in the mean time I saw in my manual that Honda Dot 4 brake fluid is recommended. Hope it helps.
Click to expand...

Thanks but I don’t think the hydraulic fluid is a problem. I’ve been using DOT 3 for years and this is the first failure. A seal has probably just worn out,
DOT 3 and DOT 4 have the the same basic ingredient with glycol based but 4 has a higher boiling point. If I want to boil some eggs must keep that mind.
 
I'd blank off the master and see if the lever hold pressure - use a 10 mm bolt if needed. More normal for the slave to fail.
 
kerbside said:
I'd blank off the master and see if the lever hold pressure - use a 10 mm bolt if needed. More normal for the slave to fail.
Click to expand...

Very good idea. I’ll give to a try. I’ll put a bolt wrapped with some Teflon tap. That should do it. I’m assuming if it doesn’t hold or pump up the master is shot?
 
Yes, that would indicate the problem is in the Master. May just be seals, so not necessarily "shot". If it does build and hold pressure, then the problem is most likely in the hose or slave...unless the clutch is just worn out, but I would guess you would have had some symptoms leading up to this if that were the case.
 
There is a "trick" to bleeding air out of the clutch system on a ST 1100. To do this successfully, you need to crack the banjo fitting up at the top, where the clutch hydraulic line attaches to the master cylinder body, and bleed air bubbles out of it there. Once you have done that, you can proceed to finish the bleeding down at the bottom end.

I am forever indebted to @paulcb for explaining this trick to me when I replaced the clutch slave cylinder when I was in Morocco last February. I spent half a day, and about a quart of hydraulic fluid, trying without success to bleed the system, until Paul made a post (post #23) explaining this little trick to me.

Have a look at posts 21 to 27 in that thread to get some context, then have a look at this post ST1100 - Replacing the Clutch Slave Cylinder, which will give you the background info that explains how I ran into the bleeding problem.

If you do what Paul suggested in his post #23, you will be up and on your way in about 20 minutes.

Michael
 
Be sure to check the Bush for wear in the lever too. It's the little brass bugger in the lever that the pushrod acts upon. I know this is no help at all but if I crack the slave open the fluid runs out, I feel blessed.
Upt'North.
 
kaplang said:
DOT 3 and DOT 4 have the the same basic ingredient with glycol based but 4 has a higher boiling point.
Click to expand...

Jim is waiting for this - "higher boiling point" is the key here and is the only fluid recommended for any disc brake system, which can generate a lot of heat in mountain riding. Not a place you want to experience brake fade.
 
I was gonna jump in and explain what Michael said in post number 8, however, after seeing the comment about the brake fluid choice, I decided to stay out of this thread ;)
 
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