Hot start problem, Checking opinions before I buy a new battery Options

[Highland]

My car starts easily when cold, but hot it has been a struggle. I put a variable resistor on the CHT as an experiment without success. Engine's not even catching.

Plugs look good, 123 distributor, blue coil, valves adjusted, runs fantastic once started.

I am using a 2 year old motorcycle AGM battery(which has been working prior to 123 distributor install). Open voltage measures at 12.6V.

I stuck a lead on the coil while cranking and voltage drops to around 10V and will bounce down to 0 occasionally if I crank for more than a few seconds. With ignition only the coil is at about 12.3V.

The blue coil is an NOS coil that I had. It's probably over 30 years old but resistance is good when cold. I did not think to measure the resistance hot, but would it make a difference? Does the insulation breakdown over time even if resistance is good?

Thinking my little battery doesn't have enough power to crank and fire the coil. Any opinions? Cranking is strong.

[BeatNavy]

It gets complicated. I spent a few minutes reading (or rather scanning) this: https://members.rennlist.com/pbanders/ecu.htm#ES

I got lost on some of the abbreviations and had a hard time following in some cases. Reading this reminds me how impressive D-Jet is from an engineering standpoint given technology at the time.

@PBAnders mentions something about a "start signal" in the context of Idle Cold Mixture Compensation and in the context of fuel pump relay activation, but it doesn't appear (best I can tell) that the ECU has a specific starting mixture circuit or input to pulse width.

If that's the case, I would assume pulse width would be driven by inputs the same as normal operation, with the two most important being manifold pressure and head temp. If the idle circuit is engaged (because the throttle is closed), then I assume IM has a large input to starting/cranking enrichment. Maybe you can glean more from reading that page than I was able to.

FWIW, my hot start problems on D-Jet were significantly mitigated when I installed my hi-torque starter. Have you tried the starting procedure Brad describes on the last page of that previous post?