JAP 4/2 crankcase material change

My JAP 4/2 engine is dated at 1940 and various publications I have found for it refer to the crankcase and sump being made from aluminium.
My crankcase and sump are cast iron? - I've searched in depth to try and find when the change occured but drawn a blank, does anyone have any information on this?

Alan

Maybe done for wartime production when Ali was in short supply? (just a guess)

Think you might have hit the nail on the head there! Just strange that I can't find any documentation on it.

Alan

Tend to agree with Matt - my Villiers V engine has cast iron crankcase and sump.

All the early Jap 4/2s where of cast iron. I have a very early 1935 engine that is all cast iron. The very early engines also had a three piece air cowling, that is the top section that fits over the head and around the cylinder, the front fan housing and a separate round removable straw guard over the front of the fan housing. These engines are extremely rare and hard to find now. The early ones as mentioned above are coming up to 86 years old. I think 1935 was the first year of production for the 4/2 model, and probably for that range of engines.