Hello
exfarmerIt must be so frustrating

I have not been able to find a specific Atco-Villiers manual.
If the compression is good, the exhaust port is clear, the
crankcase is sealing for loop scavenge, the spark is good, and plug
is known-reliable, the fuel is fresh ... then I guess a good
carby would be the next test.
I don't suppose spraying an engine starter fluid down the choke
when you open it might confirm the issue is lack of fuel ...(?)
I'm hoping an engine expert might have a simple test for isolating
the carburetor as the cause on this engine. My explanation would be
the same as Eccles from the Goon Shows ... "the wick has gone out".
I know you asked about the needle setting. I think these are the
setting for the small Atco-Villiers:-
Sorry I can't be of more help.
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Jack