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As may be observed from the illustrations, the general specification of all the heavyweight models is practically the same.
In this instance model T9 is the S.V. counterpart of the 4-98 h.p. de luxe O.H.V, model and has the same bore and stroke. Actually, apart from the engine and carburettor, the only important difference is that a three-speed gear-box giving ratios of 4-81, 7 06, and 12-85 to 1 is fitted as standard. S/C ratios - 5-53, 8-12, and 14-7.
Engine. Below the cylinder the engine is the same as the O.H.V., model except, of course, that a different valve timing is used. The piston is of aluminium alloy, and has the usual four rings. The cylinder in which it reciprocates has six broad horizontally-arranged fins, and contains the valves as shown in Fig. 16A, a special car type aluminium cylinder head being bolted to the top of the barrel with seven bolts. A copper and asbestos gasket is used between the two. The compression ratio is 4.9 to 1. As is self-evident, removal of the cylinder head does not mean unfastening the carburettor or interfering with the valves - a meritorious feature from the point of view of the rider who likes to devote a minimum of time to top overhauls. The valves, springs, and tappets are all enclosed, as shown by a quickly-detachable cover plate, no valve caps are wanted. Correct tappet clearances are -006 and 008 in. with a hot engine for inlet and exhaust respectively. Castrol "X.L." or "C" is recommended, and the magneto timing is 3/8 in. before T.D.C. fully advanced.
CARBURETTOR. The carburettor, which is bolted by its flange direct to the cylinder barrel, is a bottom feed, semi-automatic 6/004 Amal with 140 jet, 6/4 valve and needle position 3.
See also: AJS 1934 Model 9 500cc SV
