I don't know if this applies to your carbs, but you should be able to tell:
https://www.jrcengineering.com/techn...g-and-jetting/
If not, do a Google Images search for
Amal 900 series diagram and you'll get a lot of results to look at.
This description says you can clean the pilot jet by removing the air screw:
http://amalcarb.co.uk/rebuilding-mar...ic-carburetter