From someone I know who used to work on these old "pumper" "horsehead" pump engines-they would run off the crude natural gas coming from the oil well.He mentioned starting them was you stood on the flywheel and jumpted off before the motor kicked over.He said it took some practice to do that without getting hurt.I would like to see that jumping start being done.In many oil well installations those engines were replaced by electric motors designed for oil pump use.