Love those 2 speed kickbacks. My first was on my Sting Ray back in the mid 1960s, It was the fastest bike in the neighborhood because of the holeshot of the low gear. When I got to playing with bikes again about seven years ago, I started picking 2 speed KBs (most were found on Schwinn Breeze and Co-ed bikes) for the bikes I build for me. Ive built six bikes with them, three of them are RRBBO bikes. And I have seven or eight more for future projects. Most are red bands, but a couple are yellows and one is blue. The yellow band I used on my first build, my first aluminum honeycomb composite bike, has a couple of thousand miles on it and has worked flawlessly.
Ive had red bands that would develope loud squeal when braking, and shifting problems, meaning it was time for service.
Ive tried to refresh one, and it worked fine for a couple of months and then stuck in low gear. I now take them to my local Schwinn bike shop for service, cost $35 - $40, and if I have a problem he will fix it, its a good way to support my LBS (he rebuilt 4 of them for me this summer).
They do take a little getting used to, but are worth it to me.
Another thing that alot of the bikes had that had 2 speed KBs, were a front hand brake, so you could slow down with out using the coaster brake and therefore shifting when you didnt need to shift. I dont have hand brakes on my bikes, I like the clean cableless look.
2 speeds are all I need.