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New 147 c.c. O.K.-Supreme Tested by “Motor Cycling”
CONSIDERABLE interest will certainly be caused by the introduction of the first 150 c.c. four-stroke. It comes, of course, within the 15s. tax.
This machine, an O.K., which has been designed throughout as a proper miniature motorcycle, has particularly attractive lines and is an eminently practical engineering job throughout.
The engine is a side-valve 147 c.c. J.A.P., which has a bore of 51.5 mm. and a stroke of 71 mm. The cylinder head is detachable and fastened to the barrel by seven bolts, while both the main bearings and the big-end are of the roller type. The piston is of aluminium alloy and is attached to the connecting rod by a fully-floating gudgeon pin. The lubrication is mechanical, a Pilgrim pump, which is driven off the timing gear, being employed.
The frame is a modified version of the well-known duplex pattern utilized for some years by this concern. One set of tubes forms the tank rails and the saddle pillars, steel pressings being used for the fork ends and the combined gearbox hanger and rear engine plates. There is only one brazed joint on the frame; this is where the front down tube enters the head. The rest of the frame is bolted up and of particularly rigid construction.
A Burman three-speed gearbox, giving ratios of 8.5, 14.1 and 23.6 to 1, is standardized with a kick-starter and handlebar controlled cork clutch. It is operated by a long tank-side control.
Both front and rear chains are ½ in. by .205 in.
Coil ignition is standard, the Miller dynamo being driven by a 3/8-in. pitch chain from a sprocket on the mainshaft.
This drive, together with the primary transmission, is enclosed by a large cover, which is fitted with an inspection plate.
The switches and tell-tale are incorporated in the headlamp, the coil being under the tank on the front down tube.
The contact breaker is mounted on the end of the dynamo, the latter being located behind the engine, where it is well protected; adjustment for the dynamo chain is provided by swivelling the instrument.
A Saddle Tank.
A large welded-steel saddle tank, which holds 13/8 gallons of spirit, is finished in black and gold with a polished aluminium panel in the centre, presenting an exceedingly smart appearance. The oil tank, which is also welded steel, is separate and attached to the rear down tubes. It holds one quart of lubricant. In this position it forms a neat group with the toolbox behind it and the battery in front of the saddle pillars.
The rest of the specification includes Avon 25-in. by 3-in. tyres, Webb forks with pressed-steel blades and a single central compression spring, a soft-top Lycett saddle with three-point suspension, 4½ in. brakes front and rear, for each of which finger adjustment is provided, and large domed mudguards, the rear being provided with a lifting handle.
A central spring-up stand is utilized and the Amal carburetter has an air strangler for easy starting.
A point worthy of note on such a small machine is that the footrests and handlebars are adjustable.
A large cylindrical silencer of 15 ins. in length is placed at the end of the long exhaust pipe.
The wheelbase is 51 ins., the overall length 77 ins., the saddle height 25 ins., and the ground clearance 4¾ ins. The weight of the machine completely equipped is 172 lb. The price has not yet been decided, but will be of a competitive nature.
A Motor Cycling representative was privileged to try this fascinating little machine on the road and found that it was extremely lively and had a good turn of speed.
How it Performs.
The pulling powers, too, were excellent and, as was hardly surprising with so light a model, the steering could be completely forgotten. There seemed no doubt that, although most riders who purchased this type would require it mainly for short-distance utility riding, quite extensive tours could be made at reasonable speeds and in comfort
The "baby" O.K.-Supreme is a real motorcycle.
It is not possible at the moment to give details of the remaining machines in thc.O.K. range, but, generally speaking, the 1931 programme will be followed, with a number of refinements.
The neat little 147 O.K.-Supreme, the first of the 15s.-tax four-strokes. The new model is fully described above whilst its performance on the road is also commented upon.
Motor Cycling, October 14, 1931. Page 781