The ST 40 did run without the on board glow. At the very end I removed the current to the plug and it kept running. But there was a drop in RPM.

Yes it does keep running without current to the plug and it would have flown without the battery. I just used the battery to make it more reliable.

It must be the gasoline helping to keep the plug lit, because when I ran the ST on Sunny Side (which is almost all ethanol) and 20% castor, the engine died as soon as I disconnected the glow driver.</p>