This bike happened to have Invader mags and was lucky enough to find a dual flange one at a swapmeet! The sprocket is a flat (not dished) for a '86-'92 sportster. And the rotor is a 10".
 
 
 
 
 
 

The disc brake wheel requires a 3/4" diameter axle, so I drilled out the chain adjusters and the axle centering collar with a 3/4" bit on the drill press. The new axle is a Paughco  #26. Origonal sportster nut fits it.
 
 
 
 

This is the bracket I made to mount the master cylinder behind the stock brake pedal location..
 
 
 
 
 
 
 
 
 
 

Here it is mounted to the bike, it bolts to two holes in the frame used to mount the exhaust on the right, unused on the left.
 
 
 
 
 
 
 
 
 
 

With the GMA master cylinder mounted. The plunger is from a 70-79 FLH. It is accuated by an L bracket under the bolt that cinches the brake pedal to the shaft. Brake light switch is screwed into a banjo bolt adapter.
 
 
 
 
 
 

GMA caliper is an R-10 for rigid frames, thats what I had to experiment with from another bike so went with it.
 
 
 
 
 
 
 
 
 

I used 3/4" washers from the hardware store for axle spacers, 4 on the right and 2 on the left.