New guy intro

[Hunsta]

With the master cylinder, cant you source one from a bike that has dual front breaks. Ive been trying to get one for my R65 so I can run a dual disc like the LS, but they are like hens teeth over here. And that aslo includes the right side caliper. As for the forks being too high. Cant you just drop them through the triple trees a bit. Or are they just too high for even doing that?

[tenni128]

I certainly can, and will, drop them through the trees a bit. Ultimately it would be nice to have them shortened to the correct length. Not a big deal, though. I will keep an eye out for a dual master cylinder but would like to try and avoid having to source more parts. The master cylinder I have has the spot for a second line that just needs to be tapped, so it'd be nice to use it. These old airhead parts fetch a lot of money it seems!

[Hunsta]

These old airhead parts fetch a lot of money it seems!

Now there`s the bloody understatement of the year

[SteveD]

These old airhead parts fetch a lot of money it seems!

Now there`s the bloody understatement of the year

Try buying any Italian bike parts from the same era.

[tenni128]

True enough. I have a couple of Guzzis as well. I looked, just for kicks, on the price of a new master cylinder. $389/USD. Wowzers. Looks like I'll keep checking into machine shops. I emailed a few hydraulic outfits in the area that I expect should be able to help, as the usual bike shops I use didn't have the tooling to make the proper bevel for the brake line. I can always cobble a splitter together from the K100RS stuff, and use the one line, but it wouldn't be as clean of a solution.

[vanzen]

I certainly can, and will, drop them through the trees a bit. Ultimately it would be nice to have them shortened to the correct length. Not a big deal, though. I will keep an eye out for a dual master cylinder but would like to try and avoid having to source more parts. The master cylinder I have has the spot for a second line that just needs to be tapped, so it'd be nice to use it. These old airhead parts fetch a lot of money it seems!

IMO, I consider the extra stanchion length
(@ 1" above the cast upper tree to retain stock geometry)
and the fact that the stanchions can be easily adjusted for length as a method to fine tune rake & trail
to be the major advantage of the K-forks vs late R-forks –
which use the same rotors & calipers but a steel plate upper tree.
Simply shortening the tubes and tapping them for the caps without altering the internals
will affect travel, preload, spring rate, and damping characteristics.

Also, IMO, by virtue of the smaller bore, an MC intended for a single brake
works better with dual calipers than the one intended for duals.
The stock system MC to wheel cylinder ratios were far too conservative for effective braking.

See: Vintage Brake

And, it is no simple task to machine the single MC to dual MC specs.
A single MC can be used to operate dual calipers using a custom (made to your specs) brake line
that looks something like this:


See: Spiegler

[tenni128]

That all makes sense. I'd like to exhaust any reasonable possibility of having that second boss tapped out primarily, as it would be a cleaner looking install than teeing off a line. I currently have (due to an R90/6 box 'o' parts deal I bought) no less than three braided lines for use with the stock MC, and it'd be nice to be able to use them. Thanks, Vanzen, for the reassurance on my thinking that the stock MC will work with dual calipers; I had read that elswhere so it's good to hear it again. And I'll leave the forks alone. Promise.

[vanzen]

That all makes sense. I'd like to exhaust any reasonable possibility of having that second boss tapped out primarily, as it would be a cleaner looking install than teeing off a line.

Assuming an under-tank MC (and it's nasty lever feel of cable stretching)
the "T" brake line could be designed with a short leg to the MC, and two long legs to the calipers –
Appearance would be clean and not noticeably different than stock.

My plan uses a Brembo handlebar MC with a remote reservoir
mounted to the upper tree just to the right of the central tach.
A "T" brake line with one leg extending from the MC to the fork brace,
the "T" junction fastened to the back of the brace, and a short leg to each caliper from there.
(K75S forks, R1150 spoked wheel, 4-pot Brembos, 320 mm floaters, ABS removed)

[George Ryals]

You can drill and tap the second boss for 1/8" pipe thread then use a 1/8 pt male to inverted flare adapter and use the stock hose to the caliper.

[tenni128]

Well, I just got off the phone with Woody's Wheels. I'll be sending off the R100R hub and my original R90/6 wheel, where the two will be given soft music and alcohol in the hopes of mating. This should result in a new, tube-style spoked front wheel with R90/6 appearance that will fit the K100RS front end and axle. Sounds like they might even be interested in taking my R90/6 wheel on a partial trade-in. I talked to him about the caliper clearance issues, and they're going to cross spoke the hub onto a new rim blank that should suck the spokes in far enough to get the clearance I need. It's really only about an 1/8th inch I need, so it would be great if I can get that without having to mess with shimming the rotors and moving the calipers outboard.