Radial master cylinder info?

[Tricky-Ricky]

Hi, new here but not to bikes by any means, currently building a Trident T160 bobber on a budget, and running into problems with brake and clutch master cylinders not being big enough piston wise to operate the two twin piston Lockheed calipers, and the aftermarket clutch slave.

17mm pistons do not shift enough fluid for either, and i am having trouble finding M/Cs with at least a 18-19mm piston, the only ones i can find are radial on AliExspress, but i am not familiar with them, so i am looking for info about them from those that know?

I have seen piston diameters up to 20mm but they are labeled from 16x18 up to 18x19-18x20, now i am guessing that the latter figure is the bore, but have no idea what the first figure refers to?

[wr6133]

Pivot Length.

[Tricky-Ricky]

Thanks! so is that always the first or second figure, and just how does that affect feel and operation?

[Snod Blatter]

It's usually bore x ratio(or pivot distance, whatever), where 20 ratio moves the most fluid/is harder to pull and 16 moves less/is softer. You'll be wanting 18x20 but really that may not be enough, my experience of moving from a 5/8 axial to 11/16 radial (Nissin from a Kawasaki, no idea of ratio) is a significantly squishier lever, though loads of feel and power.
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1994 CB250, 1984 CBX250RS-E, 1989 K100RS, 1995 TRX850, 2016 Z250SL

[Tricky-Ricky]

Its a difficult one as i need the clutch to fully disengage before end of leaver travel is reached, so a pair with 19x20 or 19x 18 sounds like they may work, the odd thing is with the axial 5/8 M/C both worked and felt OK, yet with the Chinese 17mm axial M/Cs it was way to little movement on the clutch side, and no brake until the leaver was nearly at the handlebar.

[iansoady]

WRT the brakes, a 5/8" diameter master cylinder should be enough for 2 Lockheed calipers.

No idea about the clutch though, which must be an after market job?
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Ian
1986 Honda XBR500
1952 Norton ES2

[Kickstart]

Hi

Above comments on the 2 numbers are correct. Worth pointing out that the same applies to conventional master cylinders, just the pivot ratio is rarely if ever given. Hence while you say a 5/8 master cylinder (which is pretty standard for larger Japanese bikes) doesn't move enough fluid, it will vary with which 5/8 master cylinders.

All the best

Katy
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[wr6133]

[Wafer_Thin_Ham]

[Kickstart]

[Tricky-Ricky]

Thanks for the input guys, its appreciated, the biggest problem with using both used and aftermarket M/Cs is that without also knowing the number and size of the rotors that the M/Cs are intended to operate, its all a bit hit and miss.

The other problem is that i also need a suitable M/C for the clutch, which complicates maters further, a number of years ago i have a mate who was a MC beaker which made the mix and match game a lot easier.

On the subject of Chinese manufactured parts, i don't really have a problem, i have used lots of things manufactured in China with no worse failure rate than product manufactured elsewhere, in fact you will find that about 70% or more parts and good are actually made there including you TVs and hi-fi, tablets and laptops.


Anyway i have now ordered a set of 19x18-20 radial M/Cs from China, and fully expect them to do the job OK, for probably a lot less than buying unknown used items.

[dansp1]

https://www.vintagebrake.com/mastercylinder.htm