Model A - carburetter investigation

In a spare moment while waiting for parts I thought I would have a look at the carburettor provided with the Model A kit. I've not touched it since it arrived all those years ago:

In the last couple of days I have removed it and giving it a good clean so that I can discover what's missing and what's broken.

It's the original carburettor and is pretty worn but it cleans up well:

Standard fitting for the 1930 Model A is a 6/112 carburetter, now called a Pre-Monobloc, which is 1" throat diameter, and here is the evidence:

According to the Amal book, jetting is as follows:

• 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
• Float chamber: 14/004

The slide is really bad - probably the worst wear I've ever seen. The grooves around the top of the needle are in pretty poor shape too - we should expect this and the needle jet to need replacement

The choke slide spring appears to have been cut short - fortunately I found a spare one in the carburettor bits box.

The float chamber appears to be correct - I didn't expect the bowl to be held by those two brass fittings at the bottom - there must have been a gasket in there

Initial observations:

• The main jet is missing
• The needle looks very tired 
• If the needle is tired the needle jet will need replacing 
• We probably need another cable adjuster 
• The slide is very bad which probably means we need a rebore from Joe the Carb.
• We need to understand how the float chamber fuel feed was sealed - possibly by some sealant in the thread

That's it for now - it's back on the bike and we can start some other jobs.