Installed the transistorized ignition on my K1 yesterday. Bike suddenly came to life and starts well when cold. Idles beautifully too.
I initially ordered it for my cb350f but decided to put it on the cb750k1. I found the wires to be a bit short possibly because it was made for a much smaller bike (not sure if they are all the same or the wires are cut to specific CB's). I made it work by mounting it on the top of the airbox. Hardly visible.
This sounds like you connected the Blue/Yellow/Violet/Orange wires at the coils, and not at the points plate junction. If you install that way, yes, the wires are too short. It is intended that you should be able to unplug the wires at the top right rear of the engine, where the point plate plugs into the main harness, to make the 'instant disconnect" feature available if you ever decide to switch back.
So, the Black wire does connect at the coils, and the Green wire on the points plate, but the other 4 should connect at the junction that is just in front of the oil tank, where you will find the points-plate wires.