Model A - carburetter needs some bits...

 The Model A uses an Amal 6/112 carburettor, often known as a pre-monobloc. The Type 6 carburettor has the pilot air inlet in holes around the body and is similar to the Type 76 - the difference is that the 76 is cast alloy and the 6 is cast brass. The float chamber design associated with each of these carburettors is also quite different in that the earlier float chamber has the extension pipe banjo retained to the float chamber itself with a screwed joint.

Whilst the carburetor that arrived with the Model A is complete, it is also pretty tired. The slide is very bad, the main jet is missing and we know from experience that the needle jet and needle will be very worn as well. 

The specifications are listed here:

• Size: 1"
• Main Jet: 4/042-160 (still available new)
• Pilot Jet: none
• Needle Jet: 4/061-106 (still available new)
• Needle Position: 6/065, position not recorded
• Slide: 6/0524 - that's a #4 cutaway, or 1/4"
• Float chamber: 14/004

Folk with some experience of Amal carburettors will realize that these part numbers are used for the Type 76 and Type 276 as well - and are still available from Burlen Services, or Hitchcock's Motorcycles.

I put in an order to Hitchcock's for some bits and sent the body, jet block and jet block nut to Joe the Carb on the 23rd of July:

It came back from Joe on the 8th August with a cylindrical bore, a slide to match, and he has refaced the mounting flange so that it is nice and flat. It looks like it has been vapour blasted too:

Until I make up the cables there's not much else I can do with this carburettor (other than replace all the gaskets and fibre washers), so we'll fit it back on the bike and leave it for now.