Topic: Rear Disc Brake conversion

[Humble Pie]

Basically, can I just swap out the disc set up from a 75 SS ,,to a 75 K ? ,, also would I be able to use a disc set up with a 1970 Swing arm ? 

Thank you

[KingCustomCycles.com]

Wheel is different, frame has to have hardpoints welded for stay bar, need a mount for the resevoir, switch for light relocated, and the brake lever is different.  Swing arm can be modified but is not a bolt in swap. About an afternoons work with a mig, sawzall, hand grinder and some gloss black rustoleum.

[Roach]

if im correct you will need to change your swing arm

[KingCustomCycles.com]

Early K swingarms are narrower by about 1" but the spacers could be modified to fit.  I have gone the other way a few times converting an F to a drum rear.  Others may know more specifics. Brake light switch is inside the frame tubing as I recall on the F and outside on the K with different attach points.

[Rookster]

The sprocket carriers are the same between the K and the early F.  The axle diameter is the same as well as the wheel bearing sizes 6304 for the wheel and 6305 for the sprocket carrier.  This means you should be able to use the F wheel with the K sprocket side spacer.  You would then have to make spacers for the caliper bracket side.  Everything else should be doable.  As far as a master cylinder and brake switch.  You can use the K brake setup you have and modify the brake rod to pull a master cylinder piston.  This is actually much easier than it sounds.  You can then keep the K brake light, pedal and linkage.  I am going to be doing the drum to disk conversion this winter and have gathered a bunch on info on it. 

Here's a pic of the Hallcraft disk conversion for the CB750K:


You can see how the master cylinder mounts.  There is a bunch of room in there for it.  You need a master with a pull bracket to work the piston.  The caliper has to sit underneath the axle if you want to use the old brake stay bracket on the K swingarm.

Scott