Originally Posted by 
JDNSW
				
			 
			I am not familiar with that particular model, but the ones I have had experience with you only needed to get them up to about 1000rpm before changing. Possibly need to run a little longer in very cold conditions.
 
The whole idea was to solve the problem of starting a large diesel by hand (no electrics). An extra set of valves opened up an additional combustion space in each cylinder equipped with its own intake valves, spark plugs, manifold and carburetter. 
 
Sounds complicated, and it was. But at the time it was considered cheaper and more reliable than electric starting. Another scheme, used, I think, by Caterpillar, used a separate petrol starting engine, which was started and then engaged like an electric starter to turn the main engine.
 
John