HOME and how to join Forum Open Area General Scott topics Amal 289? Re: Re: Amal 289?

#11778
BRIAN MARSHALL
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Hi, I trust that Dave means choke diameter in his last sentence, not slide diameter, as of course slides are wider than the choke diameter, or air would leak by the sides of the slide. I have now had chance to measure three Type 29 carb choke sizes. All are brass bodied and have the primary air inlet in the choke tube rather than externally around the bottom of the mixing chamber. One carb is a genuine 29/005 Clubman carb., and it is 1-3/32″ size. Then a clip-fitting version, stamped 289/032R, is also 1-3/32″. Finally I have what was another clip-fitting Type 29 that has had a Scott three-hole flange grafted onto it, and the number stamping is no longer legible. It has a choke diameter of 1-1/4″ !!
Brass bodies continued to be made after 1933 for some bike manufacturers, including of course Scott, as even Brum Scotts have brass carbs, but they were very possibly old stock. Early post-war Vincents were also fitted with brass carbs..
The change from external primary air holes, to an internal one adjacent to the bellmouth thread, was at the behest of Government buyers, who very sensibly insisted that all the air entering the carburettor could be filtered, including the primary air.
Brian