AJS & Matchless Owners Club

The washer below the rubber sleeve on the pushrod tube does not appear in the parts lists for iron head engines until 1950 when 38-G4-E379 is mentioned (this is the flat top washer noted as also being fitted below the rubber sleeve). Then in 1951 when the alloy heads were introduced part number 016944 is listed (dished washer).
The iron head engines I have worked on I have always omitted the dished washer as it is not in the parts list and not noted any issues, if you run an iron head do you retrofit the dished washer as a later improvement or omit?

look at the part number Ducan. 38 = 1938. G4 the smallest model it fitted. E = Engine. If it also has a new part number it would be 000379. Check if the valve stem end should have a cap or not.

I can't see that it'd make any real difference either way but I for peace of mind fit the dished washer. Just in case, as you say belts and braces.

I have a dished washer fitted on my iron head bike

without the dish washer you will probably flatten & split the bottom cupped end. I found my bike like that. It had the cupped washer then a flat washer jamed in the top end