Topic: Brake fluid

[Angiey2002]

Hi Guys
Noticed a small pool of brakefluid under my bike this morning.CB550K 1977. Traced it to the master cylinder. It is leaking out of the cap??? When I took the cap off and pumped the front brake lever the fluid is flowing up from the small hole (if I pump the lever hard enough the fluid will jump out of the m/c) so I assume this is caused by pressure coming up the line and a build up of pressure is causing the fluid to leak out of the cap. Should there be pressure like this? The whole braking system has been renewed including master cylinder overhaul, lines etc.
Any pointers greatly appreciated.
Thanks

[Klark Kent]

the tiny geyser is normal.  as for why it owuld be leaking i could only suggest you make sure the rubber gasket is sitting concavely- indented toward the ground- and that it is making a good seal.  i have never had this particular problem so i could be missing somehting, but if the rubber piece is seated correctly and the top is screwed down, i can't see the mc leaking.
best of luck
-KK

[bryanj]

You just discovered the first test to see if all is OK and yes it is.

If you tighten the cap too much, or without the white plastic shaped bit it distorts the rubber diaphragm and causes a leak

[750goes]

when you park the bike - try and make sure the m/c is sitting level... and don't overfill it... plus you need a good diaphragm...

[Gordon]

If the diaphragm is in good shape and making a proper seal, you can hang the MC upside down and it won't leak.  Don't overtighten the cap.  If you do, you can tear the edge of the diaphragm.  The cap just needs to be snug, not wrenched down. 

[Angiey2002]

Thanks for your help guys. I had it tightened right down so maybe that was the problem. Have loosened it off now so well see if that does the trick. Diaphragm looks ok. Thanks again.