Front Master Cylinder.

G Dingle

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Hi All

Looking for a master cylinder for my 79 twin disk, mine is fubar.

Original size is 11/16 (17.5mm).

Heiden recommended the 13mm master cylinder, would this work?

I've had a good google and quite frankly I confused myself..........

So, what size master cylinder do I require please?

Is there a decent alternative?

Thanks guys!!
 
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http://www.vintagebrake.com/mastercylinder.htm
 
Hi All

Looking for a master cylinder for my 79 twin disk, mine is fubar.

Original size is 11/16 (17.5mm).

Heiden recommended the 13mm master cylinder, would this work?

I've had a good google and quite frankly I confused myself..........

So, what size master cylinder do I require please?

Is there a decent alternative?

Thanks guys!!
I would imagine a13mm master cylinder would work, may feel a little spongy under the fingers.
I have twin discs on my 400/4 with a standard 13mm M/C that feels that way but it definitely works.
on the other hand I have a standard set up on my Commando 5/8 MC and that feels like squeezing a brick, doesn’t stop that good.
David Silver Honda spares were selling an aftermarket M/C for a very reasonable price, around £45 as I recall.
 

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Mine, with twin discs in Euro-spec, had the original 11/16" m/c which I replaced with a 14mm m/c after rebuilding the calipers.
Brakes that made stoppies a near possiblity were the result.
Unfortunately, there was too much free movement at the lever, caused by the old design of the calipers.
So I fitted a 5/8" m/c from a Deauville and it's damned good.
 
Hi All

Looking for a master cylinder for my 79 twin disk, mine is fubar.

Original size is 11/16 (17.5mm).

Heiden recommended the 13mm master cylinder, would this work?

I've had a good google and quite frankly I confused myself..........

So, what size master cylinder do I require please?

Is there a decent alternative?

Thanks guys!!
Yes a 250 Virago Nissin used on ebay. I bought one 13mm cheap and it is great quality. It would retail for $180 ?
Cost me $20. It had a scrape on it and no one bid on it. took a black sharpie. Now the scrape is hidden.
I cleaned it out particularly the tiny holes in the bottom of the MC. Also a cheap stainless brake hose.
 
Yes the smaller MC for the American single disk works better than that monster Yamaha stuck on the twin disks. I've put thousands of miles on a front brake set up that way, some of those miles were at speed on twisties. (Blame @desmoman900 ) :sneaky:
It's a period thing; nearly all makers were trying to emulate the feel of the drum brakes the disks replaced. It wasn't til the early 80's that the change to 2 finger braking from the factory (on sport bikes) became more common. To this day pathetic front brake action on cruisers is accepted.
 
Hi all,
I also have a M/C question.. so when my bike was imported from the US to the UK it was apparently required that a second disc set up was to be fitted for road use.

Previous owner/importer fitted the twin disc option mc that’s available through Yambits.

My question.. is this really the best set MC and set up for the XS? The front brakes are ok maybe a bit wooden I’d probably like a bit more feedback if I’m honest but what’s wrong with using the small OE solid reservoir? Maybe I should also consider changing the lines for braided.

Any advice on improving this set up without going down the super modern expensive route would be greatly appreciated!

Also I’ve noticed there’s no front brake light switch or wiring! so I’m not sure whether this should be fixed to the back of the lever housing or at the splitter.

Thank you as always guys…
 

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You'll need to determine the bore size of the MC you've got then decide if replacing it will make things better. The 14mm MC that came stock on the later single disc 650 is said to work very well with twin discs. It would also give you a brake light switch and the reverse thread mirror mount.
 
Interesting; looks like you have euro fork legs, rotors, the US single rotors are a larger diameter and the caliper mounts are higher on the fork legs.
I am running twin US diameter rotors, stock calipers and a 14mm MC from a special with stainless steel lines it all works great together.
front brakes madness.jpg
 
You'll need to determine the bore size of the MC you've got then decide if replacing it will make things better. The 14mm MC that came stock on the later single disc 650 is said to work very well with twin discs. It would also give you a brake light switch and the reverse thread mirror mount.
I’m not entirely certain of the bore size as those details stamped underneath the MC do not seem to make much sense to me so without stripping the mc down who knows however, I’ve now seen what appears to be the same one on the Heiden site labelled as a 22mm bore! For years 72-76.
Heiden sells a 16mm for twin disc with the black rigid res and matching lever AND brake light switch though! I could spend a fortune in his shop.
 
Interesting; looks like you have euro fork legs, rotors, the US single rotors are a larger diameter and the caliper mounts are higher on the fork legs.
I am running twin US diameter rotors, stock calipers and a 14mm MC from a special with stainless steel lines it all works great together.
View attachment 243771
Yes that is interesting. The plot thickens, I wonder if the forks legs have been replaced though I’m really unsure as I had spent about an hour peeling off the most stickiest toughest American bumper sticker from the right fork leg that had probably baked on over a course of a few years which leads me to believe the forks are original.
I think my discs/rotors are 267 dia.
 
I also have a M/C question.. so when my bike was imported from the US to the UK it was apparently required that a second disc set up was to be fitted for road use.
Sounds like somebody spun a line of bullshit.
If the original single disc was capable of braking effectively (and it was) there was no requirement for it to be replaced with twins - it was a factory decision to fit twins to the Euro bikes, but that's all. Of course, many other models came fitted with twins and some owners took the opportunity to upgrade, as they saw it.
As I mention in my post above, fit the 16mm and be happy.
 
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