Shorten Master Cylinder

I am thinking of shortening the front brake master cylinder body.

I find with low or narrow bars the end of the casting, switch, and hose interfere, and I am unable to adjust the angle of the front brake lever the way I want.

In this photo, I would remove most of the casting to the right of the round bore:
http://www.britcycle.com/Products/06-3667A001.htm

The "plan" is to leave enough material to create a boss that will take a banjo bolt.
Or leave only the threaded hole for the brake switch, but use it for the brake line.

I vaguely remember somebody doing a mod like this.
Anybody recall the details?

Stephen Hill

(Sorry, but not interested in hearing how the mc from a Honda etc works just fine.)







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I have had this problem twice this month. There are two ways to improve this somewhat with out cutting the MC.
First, find a place that makes up brake lines and have them custom make one with a banjo. And you can shave off half the banjo bolt head.
2ND, make a spacer ( I used 1/4" aluminum ) between the MC and the switch block but I think that works on MK3 only

Why not just swap the switch and brake line positions such that the switch is furthest from the lever and brake is nearest the lever? This gave me more rotation of the MC around the UK handlebars than previously. Or does that still not provide enough for your need?

Seattle##gs, I am sure what it means to shave off half the banjo bolt head?

Toronado, I just looked at my current setup, and the switch hits the bars first. I am also running UK bars.
So yes, swapping the switch and hose might help. Can you still put the silly gumboot over the whole works when it is switched?

Stephen Hill

If the hex head of the banjo bolt is approx 8MM tall, take a file to it and shave it down to 4MM. It won't buy you much clearance but it may allow you to swing the entire MC up or down to where you want it.

Yes, the gum boot still fits OK. It needs to be rotated about the hose line 180 degrees but then it slips on with just as much difficulty as usual ;-)


You likely know this, but rebleeding system after swapping switch and hose will be easier if you use a syringe or other device to reverse bleed, pushing fluid up from bleeder screw and not down from MC...where you may force trapped air down through whole system. Also, bike on sidestand, steering hard over to left so MC is highest, then hold brake on with elastic etc overnight seems to work really well to firm everything up.