Long stroke engineering

[fido]

I really like the design of the longstroke engine. Everything seems nicely engineered. I have wondered why they changed it so much for the later engines, cost cutting perhaps?

[Brandis]

I believe they went to short stroke when everyone else did.  New metalurgy allowed exhaust valves to run at a higher temp. Short stroke gave more power for the same weight and displacement. 
One of the smart guys on the Forum will know better than I.

And, you must have a long stroke made after they sorted out the lubrication issue.

[muskrat]

G'day Fido.
I think! (sometimes)
When BSA went for the larger displacement A10 they corrected any (well most) of the flaws of the Long stroke. To keep manufacturing costs down the A7 was also re-designed so most of the parts were interchangeable, crank case, cams, followers, timing gears etc.
Cheers