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This machine, priced at the remarkably low price of £38 10s., is the second of the lightweights taxed at 30s. It is a smart little machine with quite a snappy performance, and makes an excellent general touring machine. It is capable of accelerating rapidly to the mile-a-minute mark without 'fuss.' The specification is as follows -
ENGINE. This, like all the other engines, is of A.J.S. design and construction. The keynote of the design is simplicity and sturdiness. It is a side valve, inclined single cylinder, four-stroke engine of 74 mm. bore, and 81 mm. stroke, giving a capacity of 349 c.c., or (according to A.C.U. rating) 3-49 h.p. A four-ring aluminium-alloy piston reciprocates in a cast-iron cylinder with horizontally finned, non-detachable head. The head on the T5 cylinder departs from earlier A.J.S. practice in that no longer is the hitherto special A.J.S. method of holding down the cylinder retained; this comprised a central bridge piece and two long bolts with turnbuckle adjustment. In this head large non-inter- changeable and mechanically operated valves of heat resisting alloy steel are placed side by side in deep pressed-in cast-iron guides. The large area of these valves ensures perfect charging and scavenging of the cylinder, besides giving good heat dissipation and freedom from distortion and pitting of the valves themselves.
The tappets operating these valves have, of course, adjustable heads to give correct clearances of 006 in. and 008 in. in the case of the inlet and the exhaust valves, respectively, when the engine is hot. They also have oil retaining guides (Fig. 15). A valve chest cover completely encloses the valves and springs. Internally the engine is practically the same as the 349 h.p. O.H.V, unit already described in detail. It has the improved type of mechanical lubrication, roller bearings to the big end of the connecting rod, ball-bearing main shafts, and a flat crown aluminium alloy piston. The compression ratio is 4-3 to 1. As on all present engines, the magneto is placed in a sheltered position behind the engine. The correct spark advance, which is given on page 20, can be accurately determined by means of the Vernier adjustment for the magneto sprocket. The exhaust system is similar to that on the O.H.V, lightweight. Castrol 'X.L.' or 'C' is recommended for engine lubrication.
Carburettor. This is a semi-automatic Amal instrument (type 5/148) with twist-grip throttle control. Unlike all other models it has a screw-in fastening. Recommended combination for low consumption and best performance are: Jet, 100; valve, 5/4; needle position, 4. Petrol consumption is 90-95 m.p.g.
Ignition. Either a Lucas magneto or the Lucas 'Maglita' chain-driven from the inlet camshaft, and the spark advance is 7/16 in. before T.D.C. The sparking plug is a Lodge H. 1.
The rest of the specification is the same as that of the O.H.V, lightweight (TB6) except that the three-speed gear-box gives ratios of 5.8, 9.1, and 16 to 1.
Page 20: AJS T9 4.98 H.P SV 1933
See also: AJS T5 SV 1934
