A total of eight AJS 500 cc parallel-twin Grand Prix racers were built during the project’s lifespan from 1947 to 1954 — four each of the two different types — the E90 with its cylinders raised just 15 degrees from horizontal, and the E95 introduced in 1952 with them inclined at 45 degrees.
According to the Kiwi AJS factory rider Rod Coleman, a total of twelve engines in all were manufactured, four each in 1947 (the original E90 spiky-finned design dubbed the “Porcupine”), and then in 1951 and 1953 (both years the later E95). While externally these differed architecturally, inside they all shared a common format, as well as major components such as crank-shaft assemblies, engine dimensions and cylinder head design.
The 498 cc engine’s 68 x 68.25 mm “square” engine dimensions…
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Motorcycle Mojo (Digital) - 1 Issue, May 2024