I did it on a Kulana back in the spring. I don't clearly remember how it was mounted, and I don't know if it will be the same on a Huffy. (It's likely, though. they're probably built by the same factories using the same parts)
That brake arm will have a square hole in it. this will mount on to a squared portion of the axle. There will be some sort of mechanism to hold it down. I'd guess that maybe yours is covered by a dust cap. Find that and remove it, and I'll bet you'll see what you need to underneath.
Sorry this is a bit vague. But that arm has to be a seperate piece from the axle. Find where they come together, and you'll be where you need to be.
I just bought a Huffy Cranbrook, its my second bicycle putting a motor on.
I tried searching the forums and this is the most relevant post I could find concerning my issue. I removed the rear wheel on the bike, but I can't manage to slip the rear sprocket for the motor over the hub. With the ragjoint between the Spokes and the Sprocket the sprocket just simply won't fit over the hub, it sits too far off the hub. Is this normal on this bike? Do I just tighten the bolts for the sprocket and try to eyeball it to make sure its where its suppose to be?
I had to take the coaster arm off, peel off that raised piece of metal off the arm
itself (dust cap), and put 1 of the Rubber Strips on the inside and 1 on the outside
of the wheel (spokes) to make mine work.
The reason for this was that the sprocket sat so far in, the chain would rub
the tires. Using that Rubber round strip on the outside (1 only - and the
other for the inside) the chain misses the tire and fender now.
For some reason the Cranbrook has a dust cap underneath the Coaster Arm
- it just about has to come off in order for the mounting to work properly.
Hope this helps, if any questions, let me know and i'll send you a couple of