did you ever considered a used original Cat setup?

When I first had the problem I spent some time reviewing the parts manual. I noticed that my setup was different. I thought about an original setup but decided against it due to parts availability, unknown complexity, cost, balanced against my mechanical prowess. With all that in mind I decided to just fix what I have as it work well years.

If your set up is working I would surely try to refurbish it. My question is about what looks like the tensioning system would not have any way to release the starter motor once the pony motor started. I my mind if the gas starter motor is spinning and hooked by tension to the electric motor, the electric motor will keep spinning as long as the gas motor is spinning. Sounds like its been working for a good long time and will continue to serve you well, but if you had some kind of declutching mechanism it might last long enough that the next guy could worry about it. Wouldn't be to hard to make a cam over lever for the idler mounted on the firewall that could be tripped when the gas motor takes off. Just curious and don't see anything wrong with what you have and if it works it works.

If its a starter/generator isn't it suppose to keep spinning to generate??

Sorry I was under the impression that it was a converted generator used as a starter. I guess if its a generator/starter you would want it to turn after it started.

It does continue to spin but it is not used as a generator. It is wired direct to the battery with a push button switch. Once you let go of the switch the circuit is open. There is no feed back loop to charge the battery.

If I did the cam idea to disengage the starter once the pony started, wouldn't the belt around the pony continue to rub causing a wear issue?

My guess is it was never intended to be a generator but only to use as a starter because he got tired of pulling the rope. The battery would be good for many starts without being connected to a recharging circuit. I was waiting for another regulator on my D4 and I started the pony at least 15 times and never recharged the battery.
With his setup the starter after being used as a starter would be turning but with no load (like someone pointed out previously) so would not put much of a load on the tensioner. He probably just hooked the battery to a charger every so often. Right off hand I cannot think of any starter / generators on equipment that are belt driven. Smaller ones like lawnmowers are gear driven and electronically switched from start to gen.

I have 12v on my D2 and D4 to start--and yes i seldom have to recharge them as i have no 12v generator

Cub cadet had a 3 coil regulator belt driven Starter/Generator setup - kept the battery charged as would the cat setup help some to charge battery. Bob