Bleeding Clutch After Complete Rebuild- Need advice

jim 91 st

jim 91 st

Jim 91 ST1100
Joined
May 10, 2008
Messages
44
Location
Holland, Michigan
Bike
91 ST1100
Clutch hydraulics were completely dry on my 91 (likely original... yipes!), so when I suddenly had "no clutch" this Spring, I knew I was in for a task. What an idiot to wait so long, especially since it gets a lot of rain use.

So I rebuilt the slave and master with K&L kits, cleaned them all thoroughly, slave piston looked pretty good, so I think it will be OK.

However, I am trying to bleed the thing and it is taking forever, if at all. I followed the Clymer directions and getting a tiny trickle of bubbles as I squeeze the clutch lever, over and over and over. I hold it to the bar, open bleed valve briefly, repeat. So far fluid level has gone down about 1/4" at best, but does seem to be going down a tiny bit.

Does this sound normal? Brakes were a piece of cake compared to this job. I read somewhere else about cleaning the bottom orifices of the master and I think I did that thoroughly, with a tiny pick and brake cleaner. Might this still be plugged? I sure hate to take it all apart again.

Thx!
 
I like to pump up the Lever a couple of times and quickly open and close the Bleed valve on the last stroke, closing the valve before the lever completes it's stroke. I think it pulls in less bubbles this way.
Also Try Strapping the lever shut overnight to allow bubbles to come out of the Master.
 
I've been strapping the lever to the bar (after several pumps) and going around to open bleed valve. Maybe I can try your idea with some gymnastics.

I like the idea of strapping it to bar overnight too... what do I have to lose? :)

thx
 
Whatever I was doing, above, seems to have worked! Continued bleeding (but no resistance) and I suddenly got some brake fluid, kept bleeding and it suddenly firmed up. I guess the huge air pocket finally moved through. All feels normal now, but lots of reassembly to do before I can test it.
 
Bloody Hell My clutch won"t bleed.
I drained the old fluid by removing the line at the slave cylinder, on my 93. I did this a week ago when doing the front breaks

Yesterday I Cleaned all the snot out of the master, flushed the line, and purged the slave by flushing through the bleeder to the open inlet.
I filled the reservoir and waited for it to gravity bleed the line that was connected at the master. nothing! No Bubbles when pumped. Tied the lever back and quit for the night. Day Two Fluid level in master did not fall. I pulled the line off of it and can get pressure when I thumb the outlet and work the lever. I did this a couple of times to flow some clean juice through the master and reconnected the lines still nothing. I am Befuddled
 
Bleed it at the hose/master cylinder banjo joint, just like you would at the nipple.

Check the bronze bushing in the lever. It should not have a through hole.
 
Last edited:
mr.m said:
... Day Two Fluid level in master did not fall. I pulled the line off of it and can get pressure when I thumb the outlet and work the lever. I did this a couple of times to flow some clean juice through the master and reconnected the lines still nothing. I am Befuddled
Click to expand...

Did you forget the push rod? BTDT. :mad:

I installed a new slave cylinder and a new to me used master cylinder. When I attached the hose to the slave, I opened the bleeder valve 1/4 turn. I positioned the MC such that the top of the reservoir was horizontal. Filled with fluid, grab a couple rags and the appropriate wrench and lay down and waitted. The fluid started dropping from the bleed vale. After about 10 drops, I snugged down the bleed valve. Got up and pumped the lever a couple times. Felt right so I started the motor and ran through a few gear changes. Everything seemed good so I went for a ride. Worked good!! No up and down, no pump and dump.
 
Check out reverse bleeding on the interweb thingymabob, YouTube has endless videos on this technique which may be your best bet. You're not the first to experience this issue but fortunately mine gushes out when I open the valve.
Upt'North.
 
Almost by accident I found that pulling the lever *all* the way has little effect, whilst small strokes produced significant amounts of bubbles emerging from the bore in the M/C reservoir bottom...
Once those had finally cleared I was able to bleed the system regularly...
(at the shed I've an air-powered vacuum bleeding kit avail, but one time the '94 ST's hydraulic failed at home in the basement garage, requiring an emergency fix... kinda weird overhauling master & slave in the kitchen sink, but since it's my place ... :biggrin: )
 
mr.m said:
Bloody Hell My clutch won"t bleed....
Click to expand...
I've encountered that problem before.

There is an undocumented requirement to crack the banjo fitting at the clutch reservoir (in other words, up at the handlebar) and bleed there first, then you tighten up the banjo fitting and carry on with the normal bleeding proceudre.

Here's a link to the original post made by @paulcb when he pointed this out to me... I was having exactly the same problem you describe. Click here: Bleeding ST 1100 Clutch. If you are interested, you can read more about the problem here: ST1100 - Replacing the Clutch Slave Cylinder.

Michael
 
Day Three Success !!!!! After reading all the replies this morning and reading brakes-operation-of-the-master-cylinder.159167/#post-2131632
I was able to get the air out and achieve a firm lever. Special thank's to the input from Igofar he mentioned using a guitar string to clear the compensation port. This was the key to my problem. I used the smallest wire in my Torch Tip Cleaner to clear the offending orifice .
Thank's To All
Cheers
 
its possible the hose/ lines are plugged. pull the banjo bolt off of the master, hold your finger over the hole and pump the clutch lever. that will tell you if you can get pressure from the master.
 
CYYJ said:
I've encountered that problem before.

There is an undocumented requirement to crack the banjo fitting at the clutch reservoir (in other words, up at the handlebar) and bleed there first, then you tighten up the banjo fitting and carry on with the normal bleeding proceudre.

Here's a link to the original post made by @paulcb when he pointed this out to me... I was having exactly the same problem you describe. Click here: Bleeding ST 1100 Clutch. If you are interested, you can read more about the problem here: ST1100 - Replacing the Clutch Slave Cylinder.

Michael
Click to expand...
Thanks so much for this. Had the exact same problem when I change out the slave cylinder over the weekend. I've changed brake lines before and never had a problem like this. I've once ran the master cylinder dry when I was flushing out the system and forgot to top up the brake fluid, and never had a problem like this. I was a few hours in frustration and came inside from the frozen garage. I remember reading this and came back to it as I had just opened the banjo bolt a bit but didn't squeeze the lever. I re-read this post and was in business 5 minutes later! Big thank you!
 
I don't why you guys monkey jack around with hydraulic brakes and clutches and have difficulties pumping, strapping handle down, etc.
Get a mighty vac and pull a constant vacuum. Start out with 20 psi and if that's not enough, gradually increase pressure. I run 60 to 70 psi but it sucks the master cylinder down to no fluid so having someone to pour fluid helps.
Bled my Harley, my big ass truck and jap car all the same way. No issues and solid brakes.
BTW, brake fluid should be changed every 2 years regardless because it absorbs moisture. Everytime you open a bottle or remove a lid on a master cylinder, it absorbs moisture.
Bleeding a clutch with a mighty vac should take 5 to 10 minutes. You will spend more time bolting the plastic back on.
More time riding, less time wrenching.
You can thank me later.
 
This is a variation on bench bleeding, which is a pretty standard procedure in the automotive trade when replacing a master cylinder. The instructions that come with new master cylinders often will instruct to bench bleed it before installation. Some of them will even include a little bleeder kit that screws in to the threaded outlet ports and has a few inches of tubing that routes back up to the reservoir with a clip to hold the tubes in place while it is being bench bled. The fluid is pumped through the piston bore right back in to the reservoir. This is just get all of the air out of the piston bore and to fill it with fluid before connecting the hydraulic lines to avoid pumping that air in to the system. Besides pushing air in to the system this air can also create an air lock in the master cylinder. This air lock can foil attempts at bleeding under the right circumstances.

Whenever a master cylinder is pumped out of fluid the possibility of having an air lock exists the same as with a new one. Bleeding the hydraulic lines where they connect to the master cyliner, the banjo bolt in the case of a motorcycle, is a common procedure that accomplishes the same thing as bench bleeding in that it gets the air out of the piston bore and outlet of the master cylinder so that it can pump fluid.
 
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