Breaking News - My Breaks Dont Work

[damienbove]

Once again i come to the group for help and advice.

The Front break developed a sudden fault, i have a R75/6, but it has a R75/S twin disk set up. I was riding out of my drive and the front break leaver did not return, instead it stayed by the throtle grip, i had to push it out manually, but the breaks worked fine. on the next ride when i pulled the break there was no response, but the second and third pull on the breaks pressured up and activated the front break, only for the same situation to occure almost every time i needed to break, i was able to limp home.

i have since blead the breaks, all ok but it did not resolve the issue.

so what should i check next.

I had great fun removing a fule tank for the very first time, so my skills are impoving.

[melville]

Sounds like they need a good bleeding! Probably a fluid flush at the same time would be a worthy project.

[damienbove]

thanks Melville i did bleed the breaks ran about 100ml though, shoudl i just keep going and flush through more?

[SteveD]

Is there a leak anywhere? Has the fluid volume in the brake fluid reservoir changed?

[Rob Frankham]

It sounds to me as though you either have a leak in the system or, more likely, the master cylinder seal has failed. By all means try bleeding the brakes some more to see if it helps but be prepared for a master cylinder rebuild if you can't get a firm brake.

Rob

[damienbove]

thanks Rob, the progressive nature of the pressure made me think it was something a little more seriouse than a few air bubbles in the break fluid, but i will try a more extensive bleeding this evening but will order the master cylinder rebuild kit this afternoon. I suspect i will need the R75/s kit as that is the front end i am running rather than the r75/6 bike it is.

[damienbove]

i see the kit changed the year my bike was built, but as they are not original front breaks i will need to do some invesitigation work to make sure i get the correct kit ordered. - thanks once again for all your help.

[damienbove]

thanks Steve D, no leaks, i had a good look around, so i am guessing its the master cylinder, i have ordered the kit, lets hope its the correct one.

[SteveD]

I had to replace the front brake master cylinder on my R1100gs a while back. It's an easy enough job. Use a good light to have a look inside the bore for any rough markings which might be corrosive. Some fine wet and dry paper (I used 1000 grit fr memory) wrapped around some dowel and spun with a power tool will nicely smooth anything out.

When I bought the mc kit it wasn't cheap. It seems to only need the seals replaced but you get the plunger, washers and spring too. A source for those seals would be great.

[Zombie Master]

How are you brake lines? With age the rubber lines can break down inside and rubber bits can come off and cause problems as you described. If the lines are old change them along with a master cylinder kit. Don't take shortcuts on breaks!