79 kz650c brakes to 78 650b

I have 78 kz650B and I got spare bike - 650c from 79
I like spoked wheels on 78 but I do like 650b dual brakes as well.

So, visually, looks like I can mount disks on spoked wheel. There is decorative cover which can be removed and 4 holes exposed. Mounts on forks as well.
Looks like it will work. Did anybody do this swap?

For rear though, looks like no hope.

Yes, you can put dual rotors on the spoke wheel. But the dual disc rotors are smaller diameter than the single disc. The caliper mounting brackets are moved lower down on the dual-disc fork lowers to match the smaller diameter discs.

The dual disc rotors are also thinner, therefore lighter. So you do want to use the dual disc rotors (as opposed to finding a second single-disc rotor). You just need to swap forks along with the other bits.

I found all this out the hard way when I swapped the discs onto my '79 KZ650B wheel and found that they no longer lined up with the calipers. Then I had to go find a different set of forks. Then the brakes worked really well and I was happy with it.

Well, I have whole 650C as donor, so no problem, I will take both drilled rotors.

Are you sure about fork? Visually fork on my 650B looks identical with unused mounts for second caliper

katit wrote: Are you sure about fork?

That was what I found. You have both bikes there. Measure the outside diameter of the discs and the distance from the axle center to the lower fork mounting bolts.

You will need to used the master cylinder and the brake line splitter from the C model. Take accurate measurements before doing any swaps. I think the forks tubes should be the same. But check all measurements.

Mikaw wrote: You will need to used the master cylinder and the brake line splitter from the C model. Take accurate measurements before doing any swaps. I think the forks tubes should be the same. But check all measurements.

Will re-check shortly. Calipers look great, will need rebuild of course.
Master will have to be replaced, don't think it can/should be saved. Any recommendations on dual disk masters? I see Z1 and other sell ones with round cap.
Need suggestion on good quality as close to original triangular as posible

DOHC is correct - the caliper mounts are lower on the C model for the smaller disks. The best option IMO is to get the dual disks from a KZ1000. Those disks are the correct diameter for your B model forks. and will have more stopping power than the C model because the have more leverage over the wheel. Running dual single disks will technically work but that adds quite a bit of unsprung and rotational mass therefore mitigating the effectiveness of the dual disk setup. Most 16mm Master cylinders will work - be cognizant of the mechanical ratio of the lever - the distance from center of cylinder bore to pivot of lever, this will have a significant effect on the "feel". The Brembo PS16 comes to mind, but i would compare the mechanical ratio to stock. it has a 22mm pivot offset, i think they also sell a 24mm offset version as well.

DoctoRot wrote: DOHC is correct - the caliper mounts are lower on the C model for the smaller disks. The best option IMO is to get the dual disks from a KZ1000. Those disks are the correct diameter for your B model forks. and will have more stopping power than the C model because the have more leverage over the wheel. Running dual single disks will technically work but that adds quite a bit of unsprung and rotational mass therefore mitigating the effectiveness of the dual disk setup. Most 16mm Master cylinders will work - be cognizant of the mechanical ratio of the lever - the distance from center of cylinder bore to pivot of lever, this will have a significant effect on the "feel". The Brembo PS16 comes to mind, but i would compare the mechanical ratio to stock. it has a 22mm pivot offset, i think they also sell a 24mm offset version as well.

I have part bike (C bike) so I will stick with that, I can transfer forks/tubes as well if needed. I didn't measure yet but I did put tubes to each other and they look identical. But will see