He converted to full gasoline/oil mix with spark ignition. He added needle bearings to the rod so he can run leaner oil ratios. The pumper carb makes it run more consistant with less dependance on tank position. When you run needle bearings the crank has to be a certain hardness, if memory serves me correctly around 60 rockwell. That's why he modified the crank. You can run the oil percentage higher and not do the needle bearing mod. That's what I am doing on my ST 51. You can also use a glow carb but it is more difficult to adjust and fuel draw can be an issue although it is not on my Super Sportster with the gasoline burning ST 51. The carb is more sensitive with it on gas but not so bad I can't use it. This type of mod is not for the technically challenged.

Edited to add: When converted to straight gas/oil the engine burns about half the amount of fuel it did as straight glow. The reason being, Stoicheometric fuel ratio for gasoline is 14.7:1 methanol is about 6.3:1 and nitro about 2:1. These are approximate but show why the fuel burn is less on gasoline.