Clutch slave cylinder bleed nipple seat leaking

[Shuggie]

So guys, my gear change action had gradually degraded over the 1300 miles I've ridden on my fully rebuilt 1200TS... initially I put it down to failing master cylinder seals but I've replaced the master cylinder seals and have tried the original Brembo ps15 master and a good 14mm Nissin too...I've bled it a few times over the last month.

After a 220 mile ride yesterday, I noticed a drop of brake fluid on the end of the nipple and leaking fluid track ( small) and when pulling the lever there's a tiny bubble forms on the end hole...it's letting in air but not enough of a leak to lose fluid other than a few drops...I've tried cleaning the seat with a cotton bud but it's still passing the air bubble back and forth...

I've looked at past posts involving putting in a ball bearing or blanking it off but would like to retain the nipple setup...

Best fix ideas anyone, please

 

[sfcpiet]

Tricky one...

1: The slightest damage to the seat of the nipple and/or the sealing surface in the alloy cover will cause it to leak. Is the sealing tip of the nipple in good condition? I've found nipples that had been done up so tight that their bleed bore had collapsed and therefore comprimising the angles of the sealing tip! If it still leaks with a new nipple, most likely the seat in the alloy is at fault. I'd use a 5mm steel rod ground to a taper mimicking the nipple seat and fine-grade valve grinding compound to carefully re-grind the seat. The better the rod is guided by the threaded bore, the better the chances are the seat will clean up quickly and accurately.

2: The slave cylinder as used on the 180s has thrown up many problems due to its construction. The actual cylinder is pressed into the sprocket cover and both the pressure line from the M/C and the bleed nipple need to seal onto the cylinder itself, not the housing. While the bleed nipple usually seals OK, many owners are oblivious of the slave cylinder workings and seal the pressure line via copper washer to the housing, causing high-pressure fluid to eventually find its way between housing and cylinder. This fluid may escape into the threaded nipple bore and find its way into the actual bleed hole of the nipple, creating the illusion the nipple seat might be leaking! The clutch hose MUST seal at the bottom of the threaded bore, onto the outer surface of the actual cylinder!!

The 120s are a one-piece design and do not show these failings.

piet

 

[Shuggie]

Tricky one...

1: The slightest damage to the seat of the nipple and/or the sealing surface in the alloy cover will cause it to leak. Is the sealing tip of the nipple in good condition? I've found nipples that had been done up so tight that their bleed bore had collapsed and therefore comprimising the angles of the sealing tip! If it still leaks with a new nipple, most likely the seat in the alloy is at fault. I'd use a 5mm steel rod ground to a taper mimicking the nipple seat and fine-grade valve grinding compound to carefully re-grind the seat. The better the rod is guided by the threaded bore, the better the chances are the seat will clean up quickly and accurately.

2: The slave cylinder as used on the 180s has thrown up many problems due to its construction. The actual cylinder is pressed into the sprocket cover and both the pressure line from the M/C and the bleed nipple need to seal onto the cylinder itself, not the housing. While the bleed nipple usually seals OK, many owners are oblivious of the slave cylinder workings and seal the pressure line via copper washer to the housing, causing high-pressure fluid to eventually find its way between housing and cylinder. This fluid may escape into the threaded nipple bore and find its way into the actual bleed hole of the nipple, creating the illusion the nipple seat might be leaking! The clutch hose MUST seal at the bottom of the threaded bore, onto the outer surface of the actual cylinder!!

The 120s are a one-piece design and do not show these failings.

piet

Thanks your advice is much appreciated...as it happens you kindly made me the fitting which seals itself to the cylinder, must be 18 months to 2 years ago...for some obscure reason , I didn't use it and opted for sealing the clutch hose to the casting body with a copper washer....very hopeful giving the symptoms you mentioned Piet ...any tips on using your threaded fitting as I'm going to get a new nipple and fit yours as a first step...does your fitting end bottom into the slave cylinder body?

 

[sfcpiet]

Does that answer your question? You would only have needed to fit the adapter and re-fit your existing hose, I made the adapter extra-deep to accept all manner of hose connections.

piet