Well the manual for the A12 says 43 fuel, 220 air for the pilot circuit.

I was running 42.5 fuel and 160 air and it was rich. I drilled the air jet to the datsun spec 220 and it was RICHER - does that make more sense? My idea was that the pilot air jet was to lean the idle fuel air as the size got bigger?

Yeah my next idea was to put the air jets to 160 (make sure the air passages are real clean to, they could be dirty still but I doubt it) and then try smaller pilot fuel jets. A 38 pilot would flow about....20% less then 42.5! When thinking of pilot sizes I thought that going from a 42.5 to 38 would only change the flow about 10% tops but if you work it out its about 20%.

Ive got a number 79 drill (0.368mm) which once drilled should leave about a 0.38mm hole AKA #38 jet. Time to break out the solder.

And I did get an exhaust reading too with the jets lol, I was choked with grey/black exhaust smoke (so yea it was a tad richer).