JAP Motorcycle Engines

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JAP Engines 1907

JAP 4hp and 9hp Engines, 1907

(L) The 9 h.p. 85 x 95 mm. (R) The 4 h.p. 85 x 85 mm.

JAP 1907 6hp and 8hp V-Twins

The 6 h.p. 70 x 95 mm. The 8 h.p. racer, 85 x 85 mm.


THESE engines are used on so many well-known makes of motor cycles that illustrations of the 1907 designs will, we know, be of interest to our readers.

On the left of the first illustration is the 9 h.p. engine with cylinders of 85 x 95 mm. and with heavy flywheels. This engine has automatic inlet valves and an ordinary make and break contact breaker which has been fitted to this make of engine ever since the first introduction of the 2 1/2 h.p. single-cylinder pattern. The weight is 90 lbs.

The 4 h.p. 85 x 85 mm single-cylinder engine is practically an enlarged edition of the old 2 1/2 h.p. engine with the exception of the timing gear wheels being in a separate case outside the crank chamber, and the method of attaching the inlet valve to the combustion head. The weight is 50 lbs.

The 6 h.p. twin-cylinder 70 x 95 mm. is identical with last year's 6 h.p. of the same dimensions with one exception - the flywheels have been increased in size and weight, and give a more flexible and slower running engine. The weight is 65 lbs.

Next comes the 8 h.p. twin racing engine, each cylinder measuring 85 x 85 mm. This has mechanically operated inlet valves, and is the finest example of a light racing engine made. It will be noticed that the cylinders are mounted at an angle of 90 degrees to each other which, although improving the balance, presents a certain amount of difficulty in fitting to an ordinary roadster motor bicycle on account of the extra space required for the cylinders. The weight is 53 lbs., or with heavy flywheels 80 lbs. All of the above engines, with the exception of the racing type, can be supplied with water-cooled cylinders to order.

The Motor Cycle 9th, 1907