Main jet size 1065 was "standard" but not marked on military parts (see also mysterious parts page). Main jet 170 was originally applied according to specification of 1937.
Slide should have 6/4 cut away and needle position 3 (counted from top). As from 3/11/1941, needle position changed to 2. Possibly to cater for the lesser pool petrol quality.
These are the original AMAL factory settings for WD16H.
Due to wear, age and modern petrol, things might need some tweeking for the best performance.
1065 out of stock so used a 106 [the original 1065 was worn oval], raised the needle one notch and had to up the main jet to 180, then 190 when I used the less restrictive intake mesh from Hitchcocks.The original 1940s mesh now in a jar of CocaCola being purged of cack. Interesting that the needle jet on a 276 has a wider throttle range influence then on a Monobloc and can affect the main jet and influence the mix straight off idle. Didn't expect that. Carb jet block a bit worn but it's original so...