An Entirely New Model in Addition to Existing Four-stroke Models.
ONE of the most striking departures in the O.K. programme, which we have already reviewed, is the new two-stoke, which has many features of peculiar interest. This new model is known as the Mark V., and it can be obtained as a single-geared mount, or with two-speed counter-shaft gear, or with two-speed gear and clutch, in each case the price being strictly reasonable.
The engine has a bore and stroke of 70 mm. x 70 mm., giving a capacity of 269 c.c. It is very carefully constructed throughout. The ports are of ample size, and two exhaust pipes, each of one inch diameter, ensure an absence of back pressure between the engine and the large silencer mounted in front of the unit.
The crankshaft runs in plain bearings throughout, all the bearings being long and the shaft carefully hardened and ground, points which tend to increase considerably the life of the bearings. In combination with the excellent cooling arrangements with radiating ribs extending down almost to the base of the cylinder, the lubrication system proves most effective. Oil is led direct to the cylinder from a Best and Lloyd sight feed drip, and we are told that no single instance of seizure has occurred even under most adverse circumstances.
A Senspray carburetter is fitted at a slight angle from the side of the cylinder. The magneto is chain driven, and lies high up behind the cylinder, where it is well protected from the effects of mud and rain. The two-speed gear is of the sliding dog type, and a cork insert clutch can be obtained as an extra. The drive is by belt and chain, except in the case of the single-geared model, which has a plain belt drive.
The frame is a powerful one and, in spite of the large diameter flywheel, provides a 5in. ground clearance.
All the fittings are of ample proportions The pan saddle is a luxury not too often provided by lightweight manufacturers. We were pleased to note that the rear mudguard extends below the belt, which is one of the most simple effective methods of preventing belt slip yet devised. Druid type forks provide easy suspension of the front part of this machine.
This very handy little touring mount does not, of course replace the well-known O.K. Junior Mark III. and IV., which have already been illustrated; it is purely a supplementary model. The new O.K. factory will be responsible in the future for all the products of Messrs. Humphries and Dawes.
The Motor Cycle, December 10th. 1914. p562.
