Front Brake Master Cylinder problems

Bitza · 22-06-2020, 05:33 PM

Hi all, OK I'm using an early coffin type Master Cylinder, my original cylinder marked as 93 had begun to leak and was generally well weathered, so I've bought a second hand one marked 98 and looking in better condition although there was a bit of a residue inside the reservoir. Having tried out the replacement I found it has no pumping effect, I tried pumping fluid back through the system to bleed out the air, but still nothing. Has anyone any suggestions? or experience of replacing the seals (assuming kits are available) I'm guessing there must be a circlip maybe under the rubber gaiter? All assistance gratefully accepted, as I'm a bit frustrated with it at the moment, Bitza.

350TSS · 22-06-2020, 06:30 PM

If anyone knows where to get the seals I also need some for my 750SS. I heard Powerbronze do them but have not chased it up yet as that is this winter's project

Luddite · 22-06-2020, 06:40 PM

This thread might help

http://www.ukmonster.co.uk/monster/s...ad.php?t=57129

Luddite · 22-06-2020, 06:47 PM

Quote:

Originally Posted by 350TSS

If anyone knows where to get the seals I also need some for my 750SS. I heard Powerbronze do them but have not chased it up yet as that is this winter's project

Mr Gazza sourced a replacement seal kit in that earlier thread so I'm sure he'll be able to point you in the right direction.

Mr Gazza · 22-06-2020, 08:01 PM

It's all very easy. All the answers are in that thread that Luddite linked to, so you don't have to find out the hard way like I did.

Seal kits come from Moto Rapido or Powerhouse.

Rip out the rubber boot to reveal the retaining ring, then warm the master a bit and prise the ring out carefully.

Make yourself a drift to replace the ring nice and square, the dims are in the thread and so is a description of my home made drift.
Don't welt the ring in with the drift, it's only used to push the ring down firmly and square with just a tap to finally locate it.

Bitza · 22-06-2020, 10:09 PM

Thanks for the info, The 93 version is a different casting to the 98, see inside the reservoir, also has anyone an insight to the 2 versions of the stubby push rod? the 93 has a slightly longer one compared to the ones I got with my smart new levers any thoughts? Also I'm not sure my replacement m/cylinder is duff, the no pump-action feels like something other than knackered seals, any ideas? bitza

Bitza · 23-06-2020, 12:50 PM

Just in case there's anyone still out there who can find any interest in this thread?! an update, I noticed that if I put a finger over the m/cylinder outlet and pumped in it did make pressure, so I rigged it up to a loose rear caliper and hey presto it worked fine "on the bench". Back on the bike and it feels like nothing is happening, has anyone out there any bright ideas about how to bleed etc, cos I'm really flumucked (is there such a word?) Help Bitza!

22-06-2020, 05:33 PM	#1
Bitza Bronze Member Join Date: Jul 2006 Location: Poole Bike: M900ie Posts: 468	Front Brake Master Cylinder problems Hi all, OK I'm using an early coffin type Master Cylinder, my original cylinder marked as 93 had begun to leak and was generally well weathered, so I've bought a second hand one marked 98 and looking in better condition although there was a bit of a residue inside the reservoir. Having tried out the replacement I found it has no pumping effect, I tried pumping fluid back through the system to bleed out the air, but still nothing. Has anyone any suggestions? or experience of replacing the seals (assuming kits are available) I'm guessing there must be a circlip maybe under the rubber gaiter? All assistance gratefully accepted, as I'm a bit frustrated with it at the moment, Bitza. __________________ Bitza

22-06-2020, 08:01 PM	#5
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,792	It's all very easy. All the answers are in that thread that Luddite linked to, so you don't have to find out the hard way like I did. Seal kits come from Moto Rapido or Powerhouse. Rip out the rubber boot to reveal the retaining ring, then warm the master a bit and prise the ring out carefully. Make yourself a drift to replace the ring nice and square, the dims are in the thread and so is a description of my home made drift. Don't welt the ring in with the drift, it's only used to push the ring down firmly and square with just a tap to finally locate it. __________________

22-06-2020, 10:09 PM	#6
Bitza Bronze Member Join Date: Jul 2006 Location: Poole Bike: M900ie Posts: 468	Thanks for the info, The 93 version is a different casting to the 98, see inside the reservoir, also has anyone an insight to the 2 versions of the stubby push rod? the 93 has a slightly longer one compared to the ones I got with my smart new levers any thoughts? Also I'm not sure my replacement m/cylinder is duff, the no pump-action feels like something other than knackered seals, any ideas? bitza __________________ Bitza Last edited by Bitza; 22-06-2020 at 10:12 PM..

23-06-2020, 12:50 PM	#7
Bitza Bronze Member Join Date: Jul 2006 Location: Poole Bike: M900ie Posts: 468	Just in case there's anyone still out there who can find any interest in this thread?! an update, I noticed that if I put a finger over the m/cylinder outlet and pumped in it did make pressure, so I rigged it up to a loose rear caliper and hey presto it worked fine "on the bench". Back on the bike and it feels like nothing is happening, has anyone out there any bright ideas about how to bleed etc, cos I'm really flumucked (is there such a word?) Help Bitza! __________________ Bitza

22-06-2020, 06:30 PM	#2
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	If anyone knows where to get the seals I also need some for my 750SS. I heard Powerbronze do them but have not chased it up yet as that is this winter's project

22-06-2020, 06:40 PM	#3
Luddite Registered User Join Date: Aug 2011 Location: Southampton Bike: M1100evo Posts: 2,465	This thread might help http://www.ukmonster.co.uk/monster/s...ad.php?t=57129