The 1922 Olympia Show.
Overhead Exhaust Valves.
2¾ H.P. Model.
70x90 mm. (346 c.c); single cyl. four-stroke; overhead exhaust valve; mechanical lubrication; Amac carb.: chain-driven mag.; 3-sp. gear; clutch and kick-starter; chain drive; 26x2½x2¼in. Price: Solo, £70; Sports, £72.
Martinsyde, Ltd., Woking.
No more interesting reply to the insistent demand for 350 c.c. solo machines has yet appeared than the new Martinsyde single. Following normal Martinsyde practice, the exhaust valve is of the overhead pattern. In this position, it is claimed, it gets the maximum cooling draught, which after all is a very reasonable theory. The o.h.v. gear is a model of simplicity and accessibility. The rocker pivots on an inverted knife edge, being retained in position by a light coil spring, which also keeps the tappet down. The valve stem, which has a shoulder upon which the rocker end abuts, extends through a cover plate in the head to the end of a leaf spring. This cover plate, which carries the knife edge bearing, is readily detachable, and thus the complete valve gear may be dismounted very easily. The exhaust port is well ribbed throughout its length. Otherwise the engine is not unconventional, although the method of driving the Showell oil pump from an idler sprocket on the magneto chain, the pump being enclosed in the chain case, is certainly worthy of note. The fuel tank fixture by means of a concealed clamp is also ingenious.
An internal expanding brake is fitted in front, but a dummy belt rim is employed in the rear, which, after all, is a system that has many advantages.
In a sports form, a Ricardo aluminium piston, a close ratio Sturmey gear box and a racing Amac carburetter are fitted, resulting in an extremely attractive looking "speed iron."
6 H.P. Model.
70x88 mm. (678 c.c); V twin cyl. four-stroke; overhead exh. valves; foot pump lubrication; Amac carb.; chain-driven mag.; 3-sp. gear; clutch and kick-starter; all chain drive; 26x3in. tyres. Price: £125.
The "Quick Six" Martinsyde, which is shown as a solo machine only, remains substantially unchanged. Its price, with an 80 m.p.h. guarantee, is £135.
On the touring standard sports and tradesman's carrier sidecar outfits the new valve gear is the chief alteration of importance if we except the new prices, which are identical for the three - £ 130.