Leaking brake master cylinder

newbuild100

Well-known member
UKGSer Subscriber
Joined
Jun 24, 2009
Messages
746
Reaction score
0
Location
UK
Bike is a 100GS, 93 model. I seem to have a leak around the base of the front brake cylinder. Is there some kind of seal in there at all ? Can it be cured ? (if so, how doas the actual res fix to its base ???)
 

Attachments

  • IMG_0791.JPG
    IMG_0791.JPG
    132.4 KB · Views: 174
Oops, sorry picture is 90 degrees out (Before someone comes along and says "no wonder it leaks " !!!
 
If I recollect correctly (unlikely!) I think the 2 or 3 screws that hold the cap on also secure the resevoir to the cylinder - give them a tweak tighter to see if that cures it, if not there is a seal/o ring of some kind in there that will need replacing.....
 
If I recollect correctly (unlikely!) I think the 2 or 3 screws that hold the cap on also secure the resevoir to the cylinder - give them a tweak tighter to see if that cures it, if not there is a seal/o ring of some kind in there that will need replacing.....

He's right...usually the single rubber seal fails
 
Actually, i have tweeked the cover screws, but to no avail. I guess its a new seal then ?!
 
Thanks folks
Anyone gota part no off top of their heads ?
 
I cleaned one up to stop a leak two weeks before going to france. It let rip again on holiday and I had to come home two days early. To be honest with you for the £100 or so for a new one I wouldn't bother. Fit a new one and you wont have to worry for another 20 + years.
 
My experience is the same as Robs, lasted a few weeks longer but end result was the same.
12 mm cylinders might still be available too, so you could treat yourself to a better brake too !
 
Cheers for all answer folks. I here what you guys are saying about cleaning the res up etc but for the attention of Rob Farmer . . . . .isnt a new seal better than £100 for a new reservoir !!! (Or are you saying a new seal wont cure the problem ????)

I cleaned one up to stop a leak two weeks before going to france. It let rip again on holiday and I had to come home two days early. To be honest with you for the £100 or so for a new one I wouldn't bother. Fit a new one and you wont have to worry for another 20 + years.
 
Cheers for all answer folks. I here what you guys are saying about cleaning the res up etc but for the attention of Rob Farmer . . . . .isnt a new seal better than £100 for a new reservoir !!! (Or are you saying a new seal wont cure the problem ????)

if it is just the seal but you tend to find there's corrosion as well.

Its your call of course.
 
Had the same problem with mine and tried the 'quick fix' which was a complete waste of money - have a browse at the Motorworks website (make sure your sat down first:eek:) and bite the bullet :thumb2
 
Well, I could change the seal if I could get to it BUT, the res dosent seem to want come off its base. Are they usually tight to get off ??????
 
Well, I could change the seal if I could get to it BUT, the res dosent seem to want come off its base. Are they usually tight to get off ??????


Those three long screws and a vertical plastic shaft with just the rubber 0 ring on it.... just make sure there isn't a small grub type screw underneath !
 

Attachments

  • DSCF0409.jpg
    DSCF0409.jpg
    209.3 KB · Views: 99
The small screw at the top of the picture is the one , it screws into the base of the fluid reservoir and stops it coming off accidentally when you remove the three top screws!
The problem is that water or whatever wicks in between the reservoir and the master cylinder and sits in the well above the O ring, eventually corroding it enough that it starts to leak.
But by the time you have cleaned off all the corrosion and pitting there is a real possibility/ probability that the O ring wont fit tight enough to form a reliable seal.
The rest of the master cylinder is usually close to worn out by the time this happens anyway, so trying to bodge it doesnt really make a lot of sense, apart from the safety angle, and if you order a 12mm as a replacement you will have 20/25% more breaking power as a bonus!
 


Back
Top Bottom