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Clutch Slave Cylinder: New Banjo Leaks


spacewrench

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spacewrench

During reassembly of my R1100S after replacing the clutch disc & input shaft, I decided to replace the clutch line, because the old one looked like this:

OldClutch.thumb.jpg.56467f1a1d06ddc78f6c7f06dee09da7.jpg

The new one looks like this -- much better, except it leaks like a sieve.

NewClutch.thumb.jpg.ba419d39d78cb8f2f436989104e49e64.jpg

The new line is from Spiegler, and the banjo fitting is thicker than OEM, but the OEM banjo bolt still shows 5-6 threads and tightens down OK on new crush washers.  I tried re-seating with new crush washers, but absolutely no change.  The system doesn't hold enough pressure to disengage the clutch, fluid just leaks out at the bottom crush washer.  (The master-cylinder end is fine.)

 

Any ideas to troubleshoot or fix?  The banjo surfaces and the slave cylinder mating surface are clean and smooth.  I just don't see how it can leak there.

 

I'm going to try tapping a plain block of aluminum and hooking the slave-cylinder banjo to it...it should hold pressure and feel like a really solid bled brake.  If it still leaks, I guess it's a bad banjo.  (There's a bit of scoring inside the banjo, but no damage to the sealing surface.)

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6 hours ago, spacewrench said:

During reassembly of my R1100S after replacing the clutch disc & input shaft, I decided to replace the clutch line, because the old one looked like this:

 

The new one looks like this -- much better, except it leaks like a sieve.

 

The new line is from Spiegler, and the banjo fitting is thicker than OEM, but the OEM banjo bolt still shows 5-6 threads and tightens down OK on new crush washers.  I tried re-seating with new crush washers, but absolutely no change.  The system doesn't hold enough pressure to disengage the clutch, fluid just leaks out at the bottom crush washer.  (The master-cylinder end is fine.)

 

Any ideas to troubleshoot or fix?  The banjo surfaces and the slave cylinder mating surface are clean and smooth.  I just don't see how it can leak there.

 

I'm going to try tapping a plain block of aluminum and hooking the slave-cylinder banjo to it...it should hold pressure and feel like a really solid bled brake.  If it still leaks, I guess it's a bad banjo.  (There's a bit of scoring inside the banjo, but no damage to the sealing surface.)

Morning  spacewrench

 

If it tightens down OK then the problem is usually due to a few things, the sealing surface of the slave is compromised, or the sealing surface of the banjo is compromised, or the sealing surface of the banjo doesn't match the crush washer,  or the side of the banjo is contacting something causing it to tilt or not tighten down evenly all the way around.  

 

I had a line years ago leak right where the metal line was welded to the banjo spool & the fluid ran down & around the lower crush washer looking like it leaked there (just something else to look for). 

 

 

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spacewrench
18 hours ago, dirtrider said:

If it tightens down OK then the problem is usually due to a few things, the sealing surface of the slave is compromised, or the sealing surface of the banjo is compromised, or the sealing surface of the banjo doesn't match the crush washer,  or the side of the banjo is contacting something causing it to tilt or not tighten down evenly all the way around.

 

I faced an aluminum block, drilled & tapped for M6, then hooked the clutch line to it with a couple of annealed copper crush washers.  It held pressure like a champ.  So I annealed a couple more washers and reassembled with the clutch slave...fluid just pours out (it leaks out pretty quickly just from the pressure of the master reservoir being higher than the slave!)

 

I looked pretty closely at the banjo & slave sealing surfaces, but I'll check again for something causing the banjo to tilt.  Maybe there's a bit of webbing adjacent the slave orifice that's keeping the banjo cocked or something.  The clutch worked OK with the rusty OEM line a couple of months ago when my input shaft went bad.  I had been hoping to get the clutch sorted so I could put the rear frame & swingarm back on!

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1 minute ago, The Fabricator said:

Bolt bottoming in threaded hole.? Try more washers.

Banjo surfaces not parallel? 

 

Afternoon Fabricator

 

He says the new line is from Spiegler, and the banjo fitting is thicker than OEM, but the OEM banjo bolt still shows 5-6 threads. 5-6 threads won't bottom out. 

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The aluminum banjo fittings from Spiegler (and others, too, presumably) are softer that you'd think, in my experience.  While installing Spieglers on my '99 S several years ago, my brother, a very well experienced professional Triumph motorcycle mechanic since the early 70's, lightly gripped a banjo with flat-faced parallel-jaw pliars to give it a twist and we never did get that banjo to seal again.  Had to order another line.  It doesn't take much to do a number on the surfaces.  

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spacewrench
12 hours ago, Lowndes said:

...lightly gripped a banjo with flat-faced parallel-jaw pliars to give it a twist ...

 

Speigler ships a plastic clamp to hold the crimp fitting, and a plastic stick to put through the banjo to twist with.  No more worrying about pinching the crimp too hard and screwing it up, or nicking the banjo by twisting it using a screwdriver shaft!

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spacewrench

Problem was a stop on the clutch slave casting, which kept the Spiegler banjo off-center or cocked and wouldn't let it seal.  I filed it down and everything's copacetic.  The rear frame is a bitch to line up too, but it's back on except for torquing all the bolts carefully.  I hope to have the wheels on and the bike back in my garage tomorrow, so I can try to get the repair finished up and go play in traffic next week.

 

 

IMG_20200523_134714.jpg

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7 hours ago, spacewrench said:

Problem was a stop on the clutch slave casting, which kept the Spiegler banjo off-center or cocked and wouldn't let it seal.  I filed it down and everything's copacetic.  The rear frame is a bitch to line up too, but it's back on except for torquing all the bolts carefully.  I hope to have the wheels on and the bike back in my garage tomorrow, so I can try to get the repair finished up and go play in traffic next week.

 

 

 

Morning  Spacewrench

 

Glad you found the problem.  

 

It was kind of pointing to something like that after  you said   "I faced an aluminum block, drilled & tapped for M6, then hooked the clutch line to it with a couple of annealed copper crush washers.  It held pressure like a champ". 

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