Gasoline use in a spark ignition air cooled engine is limited to about 9.5:1 CR to avoid detonation. That is how they are getting gas to fire W/a glow plug. Basically what you then have is (somewhat) controlled pre-ignition.

I fail to see the allure of running gas in GI (glow ignition) engines unless it us so small that CDI is not practical in the appropriate size airframe due to space limitations.