Many many thanks Ron.
I presume that missing this will not have any impact on the performance.
Quite an easy thing to make. So I'm wondering if I should just make one.
I think that the spacer is to distance the exhaust valve spring from the cylinder head, the exhaust valve side would probably be hotter than the inlet side. AMC motorcycle would not have fitted it if it was not needed. Possibly wartime pool petrol used at time burned hotter than more modern fuels
Well I still don't get it. The top and bottom cups and collars for both the inlet and exhaust are identical. So what is the spacer actually for? As proven, the engines seem to run perfectly well if it's left out?? Ron
If you omit the spacer you need a bigger indent in the bottom collar so that it seats on the head instead of wobbling about on the valve guide which protrudes 9/16s of an inch if you read the drawing.
I think you're wrong Ken. The collars are the same for both valves and will drop down over the guides onto the head, however far the guides protrude. Ron