My bad. You are correct.
I misread it.

 

nope, pretty good sign that it is not the battery...

 

The OP hasn't exactly specified whether the engine cranks freely, or whether it's a kickback issue when warm. If it's a kickback issue, a fresh battery can often solve the problem.

Another issue can be a tune with too much igniton advance at startup, which can also cause the engine to kick back (fire backwards, against the starter).

 

Not sure what you mean by "kickback issue." To me, it seems to crank freely until it grinds and I get the nasty metallic noise. I did a little over 150 miles today while running errands and joyriding. Tried what I am calling the "quick start" method, where you don't wait for the light to go out. Worked 50% of the time.
I think I will post a video tomorrow. Though most of Superglide owners seem to be getting some version of this or another....also, I have not yet put a tune on the bike. Stil factory on that front.

 

This is most definitely a battery issue. Both my bikes do this if the battery is low.
It will either go CLUNK and the lights will go out and the odometer display goes to the main mileage read out, from clock, rpm/gear or whatever it was set to, or it will spin and not start first attempt.
Never ever does it if I've had the battery on trickle charge overnight. Hot starts are worse.
My old FB did this just before the battery gave up completely. Never did it again after I put a high output battery on it.
The standard Harley batteries are the cheapest ones they can get away with supplying from new. Okay in good weather, but even a hint of cold temperature really saps the power.

 

I had simular issues. My bike would fire right up cold fresh off the tender but started having issues after it was warmed up. It would turn over a revolutions and stop until I let off the start button and tried again... it would eventually restart on the 3rd or 4th try. I replaced the battery and starts fine now. The first thing I would do is chech all your battery connections, if there good have the battery load tested and go from there. I never experienced any clunking noises.

 

The engine fires before top dead center. If the engine doesn't have enough rotational speed, or the battery doesn't have enough power to push the engine past top dead center to the point where the the pressure from firing will spin the engine forward, the pressure will stop rotation, or cause it to spin backwards (kickback), making the starter spin backwards too.

It could be a little dangerous and painful on the old kick start bikes, when that lever came back up on you.

The burn speed is slower on a cold engine, so there's less of a pressure rise before top dead center to resist rotation, or push the engine backwards. That's why the issue shows up more on a hot engine.

 

Put a multimeter across the battery terminals and crank it over and eliminate the battery as the cause...either it stays above around 9.5 vdc during the crank cycle or it drops below around 9.5 vdc...too simple to check and eliminate.

Definitely need a video...some of the symptoms described are not too much so clear.

 

Be interesting if it was the Cyl. Temp sensor on the front cyl. not giving the ECM/ECU the correct information for a hot start.

 

The sensor errors would leave diagnostic error codes.
I though the crankshaft position sensor but reading I see that that would be more apparent at higher speeds.
I only experienced error codes once and you would see the check engine light stay on.
Wouldn't hurt to check the codes anyway.