John A. Prestwich and Co.

JAP OHV Engine 1903

The makers of the J.A.P. engine are exhibiting at the Stanley Show four or five motor bicycles, each fitted with their different sets. The new 3½ h.p. engine has several new features, the inlet and exhaust valves being both mechanically-operated by a single lift rod. This rod, as will be seen in our illustration, works up the side of the cylinder, and operates a centrally pivoted lever on the top. All long port holes have been avoided, and the valve seats are both independent of the cylinder. The cylinder itself is an uniform cylindrical casting without any side projection whatever, and, therefore, is free from any distortion or unequal heating. The valve springs being on the top of the cylinder are exposed to a cool current of air, and, therefore, will be most unlikely to lose their temper through heat. By adopting the above method for operating the inlet valve, no extra mechanism is employed. The firm are also exhibiting a new sparking plug and accessories.

The Motor Cycle, November 18th, 1903. Page 797
Stanley Show 1903

John A. Prestwich and Co.,

Tottenham, N., are exhibiting one machine fitted with B.S.A. spring frame, and a motor set of their own make. The details of this new machine were fully described in our last issue, the principal improvement for 1904 being a 3 h.p. engine with, mechanically-operated inlet and exhaust valves fitted on the top of the combustion head, one earn and rod working a lever across the top of head and opening and closing both valves. (Stand 163.)

The Motor Cycle, November 25th, 1903. Page 827
Stanley Show 1903

Messrs. J. A. Prestwich will exhibit at the Stanley Show. The display will include several machines made up of the various component firm's parts, fitted with the J.A.P. motor sets, namely, 2.5 h.p. inclined motor with surface carburetter; 2.5 h.p. inclined with spray carburetter; 2.5 h.p. vertical motor with spray carburetter; and also the new 3.5 h.p. motor. This engine has several new features. The valves are placed on top of the cylinder, and are secured by one central stud. The unions can be twisted in any direction to facilitate fixing of various silencers and carburetters. The valves are worked by a single lift rod. All long ports have been avoided, and the least possible area in the combustion chamber is exposed to the flame, and the exhaust gases are carried away from the cylinder on leaving the exhaust valve; thus the engine will keep cooler than with the usual arrangement of valves. The valve seats are independent of the cylinder. The cylinder is a uniform cylindrical casting without any side projection whatever, and thus is free from any distortion and unequal heating. The valve springs being on top, are exposed to the free current of air, and do not lose the temper. The inlet valve is operated mechanically, without extra mechanism.

The Motor magazine, 18th November 1903