Monday, August 24, 2009

The 276 Amal Carburettor, from the early 1930's into the early 1950's......

Amal Ltd., until recently at Holford Works, Perry Bar, Birmingham, UK. was a conglomeration of several carburettor manufacturers from the 1920's , such as B & B, AMAC, Binks and I don't intend to get into the reasons, date etc for this amalgamation, rather to discuss the model AMAL used on most British Motorcycles from 1933 into about 1955.
Why you may ask....?
Well I had purchased all the literature of a Sydney Motorcycle accessory house when they closed in the 1990's after trading from onwards from the 1920's.
W.F.Omodei Pty.,Ltd, more easily known as Omodeis.....
There was a lot of Amal stuff and when I got it, a cursory glance through it revealed catalogues for the many Amal Carburettor types and I intend to feature these types...Amal TT, Amal GP, Amal GP2 and the earlier Amal type 27 track carburettors in later blogs.
Recently I noted some correspondence that had been overlooked until then...I've included the seven pages below which is a letter from Amal to W.F. Omodei dated 30th December 1946, together with Carburettor Service bulletin no.1 and no.2.
These are a sort of "Rosetta stone", in that they reveal why Amal changed the design of what we will call the 276 carburettor, although pre-war they were know as "76" type, then the "276" type.
More importantly there was a change of where air was drawn into the pilot system of these carburettor types and as such they are not fully interchangeable with the body or the internal jet block.
Many of these carb.types are found in autojumbles in pieces ...I had a heap of dismantled bodies, jet blocks etc, of both types and was unaware of the difference, although I noted holes around the body below the induction area on some.
Mismatch and you have the problem of getting the carburettor to run properly.
It seems various motorcycle manufacturer's war departments, who had started into war work early had requested special carburettor bodies without holes so that air would only be drawn through the main venturi into the pilot air holes and with their special air filter for the expected desert use of the bikes, would ensure clean air into the carburettor and thus the engine.
Omodies noticed this on their first shipment of spare parts from the UK in 1946.
Interestingly, the other Sydney firm, Allparts had started making Amal copies with spare parts in brass during the WW2.
Below are Amal sectioned drawings of the two types....
Left click on images to enlarge.
Letter to W.F.Omodei...

Service Bulletin No.1....

Service Bulletin No.2, 26.03.1947....

July 1936 parts drawing and caburettors,showing holes in the body.

Illustrations from a Velocette war edition instruction manual for the MAC 350cc.

Illustration from a 1954 Amal catalogue.

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