Amal carburetor information
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
Contributed by Joe Jump on the old Yahoo! Loopframe_Guzzi news group (which has now moved to Groups.io).
Joe describes the Amal carburetors used on the late Eldorado models.
Those Amals are 930's - same stuff used on Nortons, BSAs and Triumphs post 1967-68. The numbers following the dash (after 930) defines the specifics with respect to main/idle jets, slide cut-away and needle taper/position. Don't worry about that - just replace what you remove with the same parts which have individual IDs. The nylon screw that broke off in your hand is a bowl drain/main jet access screw. Parts for these are plentiful. There is a shop somewhere in Florida (Tampa area) called MAP (Made Across the Pond). They will have everything you would need. Do a Google search. And I'm sure you could find the parts in Daytona if you looked in the Yellow Pages.
I run 930s on my Norton. I had the carbs done by AMR in Arizona. Instead of sleeving the slide, they bored the body to accept Mikuni slides which are hard chrome plated brass. You loose the choke but I've found them to be unnecessary with the ticklers. I've put 20k miles on them and they still work great. Amal needle jets and needles are known to wear kinda fast - recommended replacement every 10k miles for precise metering.
One other thing to watch - the float hinge pin can vibrate (British twin) and actually wear an indentation into the bowl gasket. When this happens, the float can buzz around a bit more than normal and cause the fuel in the bowl to splash out through the tickler button and perhaps affect mixture too (too high of a fuel level in the bowl). I had this problem and resolved it by slightly pinching the tabs in the bowl adjacent to the float hinge pin to keep it captive in it's slot.
Lots of people curse Amals. They are simple units and once they are sorted with dissimilar metals between the body and the slide, updated with Viton tipped float needles, and the idle jet is opened up/cleaned (bread wrapper twist tie and Gummout spray works great for this), they work good and last a long time. Just my opinion.