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Yea going the system change is another entire approach. It’s a project in itself. Tossing money in this range should be mapped out first. @silentservice703 has it right of course, if your oem is avail install again.
 

· Old Wing Nut
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I believe you said you disassembled and cleaned the master cylinder.... Perhaps the problem is there. You can have a piston cup that isn't sealing inside and not see or have any leakage.
The piston moves back and forth but doesn't produce significant pressure when pushing fluid against the slave cylinder piston and clutch springs.
 
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2010 Brutale 990R
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53 Posts
Discussion Starter · #28 ·
I believe you said you disassembled and cleaned the master cylinder.... Perhaps the problem is there. You can have a piston cup that isn't sealing inside and not see or have any leakage.
The piston moves back and forth but doesn't produce significant pressure when pushing fluid against the slave cylinder piston and clutch springs.
That's a good suggestion, I will take a look today when I get back from work 👍
 

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Discussion Starter · #30 ·
Ok So its sort of good news.
This afternoon I stripped the master cylinder and seals are the right way round (EBBO that's for you :) ) I had a good look and everything and it all looks to be in the right place and no nicks in the seals. Piston is clean and spring is springy :unsure:
Thought about putting the old slave back on but didn't, the reason for the replacement in the first place was that the original was leaking past the seals and so I didn't want to potentially introduce another leak into the system.

Everything back together I filled the system, opened the Stahlbus bleed valve 1/2 a turn so it works on the one-way valve.
I fixed one end (wire tied it also) of a clear tube to the Stahlbus bleeder and fixed the other end to the inlet of a large syringe (without the plunger in it). Then I had a pipe from that to the master cylinder reservoir.
So with the syringe half full of fluid and the top pipe leading to the reservoir I start the game.......:p

I started pumping the lever. Every time I pulled the lever the Stahlbus bleeder 'one-way valve' let some fluid out and filled the syringe and in turn filled the master cylinder back up with the right amount. Any air would go into the syringe canister and not into the pipe leading to the master cylinder.

I pumped that lever for 90 minutes.....slowly, fast, half pull, full pull, you name it, I did it.......for 90 minutes :ROFLMAO:
My grip was always strong but is now able to crack coconuts.

So the outcome of this (other than having a good grip) I still had tiny bubbles of air in the tube.

I then decided to remove something else from the equation, with it all still piped up I took the slave off to have a look for any leaks (I know the slave is new, but you never know) it was all good in there so back it went. (y)

This means master cylinder or hose. that's all that's left. I cant see an issue with the hose but I will replace for new as it will be another easy thing to remove from the equation. (if anyone knows the spec, length, good manufacturer please let me know) I'll put in a new bleed valve at the top also (MC end) and I've ordered some new piston seals.
I have no external leaks in the master cylinder so I'm assuming I'm not getting the pressure needed on one or both of the piston seals?

I know its not fixed, but it is good news as I have a definite air leak from somewhere so I have something to work towards.
I hope that all made some kind of sense, If you think I'm way off let me know. As always thanks in advance for any help you guys have (y)

Si
 

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2012 Brutale 1090RR
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Pity it's the clutch, I had a front brake that wouldn't bleed up once, in the end I went for a ride and it bled itself, the trapped air must have wound up in the master cylinder.
 

· Vendor
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5,937 Posts
Before you spend any more money let's test the master cylinder.
Find a bolt that is the same thread as the master cylinder banjo bolt.
Cut the bolt so it's 1/2 inch long. Add a copper washer to the bolt, screw it into the master cylinder and tighten. Plenty of rags around the banjo.
Bleed the master cylinder by pulling the lever, open and close the bolt, 3 or 4 times, the clutch lever should be hard with No movement at all. If it is still soft or creeps down re-kit the master cylinder or buy a new one.
 

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Discussion Starter · #35 ·
Before you spend any more money let's test the master cylinder.
Find a bolt that is the same thread as the master cylinder banjo bolt.
Cut the bolt so it's 1/2 inch long. Add a copper washer to the bolt, screw it into the master cylinder and tighten. Plenty of rags around the banjo.
Bleed the master cylinder by pulling the lever, open and close the bolt, 3 or 4 times, the clutch lever should be hard with No movement at all. If it is still soft or creeps down re-kit the master cylinder or buy a new one.
That's a great idea mitchy. I'll get that sorted ont this weekend and let you know. Thanks 👍
 

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Discussion Starter · #36 ·
Before you spend any more money let's test the master cylinder.
Find a bolt that is the same thread as the master cylinder banjo bolt.
Cut the bolt so it's 1/2 inch long. Add a copper washer to the bolt, screw it into the master cylinder and tighten. Plenty of rags around the banjo.
Bleed the master cylinder by pulling the lever, open and close the bolt, 3 or 4 times, the clutch lever should be hard with No movement at all. If it is still soft or creeps down re-kit the master cylinder or buy a new one.
I did just as you said Mitchy and found that I was loosing pressure in the lever somewhere. So striped it all and found the smallest hole in one of the piston seals.
While waiting for the new seals to arrive I ordered a new hydraulic clutch line from Hel. It wasn't expensive and I had it made to order in under 2 days. (The old one was looking a little messy and corroded so why not)
I now have a bleeder at the master cylinder and all new copper washers etc.
Sadly I only had a couple of hours to put it all together this afternoon, so I will fill and bleed it tomorrow and report how I got on.
Thanks for all the help and fingers crossed it should be an issue once filled.
If it doesn't go well it's getting some money thrown at it in the form of some radial MC's :D

Thanks again

Si
 

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Discussion Starter · #39 ·
Glad you found it. My enough to drive you nuts.

My rear brake just lost pressure today. Grrr
I haven't had any time to get it sorted out. It's all together but no the to bleed and test it.
I have been really busy with work.

Hope the rear brake ends up being an easy fix. Thankfully we don't have abs to think about 🤣
 

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2010 Brutale 990R
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Discussion Starter · #40 ·
Hi all
Just to let you all know, the clutch hydraulic issue I had is now sorted. It bled up a very easily, its working well and no leaks.
I took the morning off work to get this sorted out, I couldn't have it just sitting there waiting.

Thanks to all those that helped me with this. (y)
I hope I can help you all someday in return.

Si
 
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