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SOHC.co.uk Forums => Other Bikes => Topic started by: mike the bike on January 18, 2015, 04:33:57 PM

Title: master cylinder
Post by: mike the bike on January 18, 2015, 04:33:57 PM
I'm trying to sort out the brakes on a 650 Katana.   The calipers are all sorted but I can't get it to bleed..  Pumping the lever does nothing.
I slackened off the master cylinder banjo, pumped away...nothing.
I fitted a brake repair kit, checked the bore is OK,  made sure the wee holes aren't blocked and it still doesn't pump fluid.
I must be missing something,  but what?
Cheesed off and left the shed to the penguins.
Title: Re: master cylinder
Post by: Bodd on January 18, 2015, 06:29:13 PM
Is it the front or rear brake ? If it's the rear and the master cylinder is like on my RD where the piston is pushed up into the cylinder you may have to back fill it with fluid, there is an explanation of how I did it towards the bottom of this page (http://www.skylinesoftware.co.uk/rd8.html).
Title: Re: master cylinder
Post by: Trigger on January 18, 2015, 06:38:40 PM
It has a air lock in the cylinder. Try tapping the brake lever like a mad man.
Title: Re: master cylinder
Post by: mike the bike on January 18, 2015, 07:07:07 PM
It's the front one.  I'll try forcing brake fluid up from the bleed nipple to purge the air out.  The air lock theory sounds likely.   Thanks guys.
Title: Re: master cylinder
Post by: Bodd on January 18, 2015, 07:27:31 PM
This works for air locks.

http://youtu.be/Jf1dBSMjr54
Title: Re: master cylinder
Post by: Trigger on January 18, 2015, 07:35:06 PM
This works for air locks.

http://youtu.be/Jf1dBSMjr54

Wait overnight? Know that trick but, tap the lever really fast has never failed me. ! 10 minute job ;D
Title: Re: master cylinder
Post by: Bodd on January 18, 2015, 07:43:37 PM
I find the fast pump method agitates the fluid and just makes smaller bubbles, the 24 hour method slowly squeezes the air lock out.
Title: Re: master cylinder
Post by: mike the bike on January 18, 2015, 08:03:02 PM
It looks like a good technique.   My first problem is getting the airlock out of the master cylinder in the first place.  I'll use a peristaltic pump (I've got loads in the van) to pump fluid upwards, then I'll do the cable tie on the lever overnight to shift the last of the air. 
Thanks for your suggestions.
Title: Re: master cylinder
Post by: LesterPiglet on January 18, 2015, 08:10:26 PM
In the past I've resorted to removing the caliper/s and raising them as high as I could and try to bleed that way or leave overnight.
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