The 1-cylinder, 4-cycle, air-cooled engine has a 3 5/16-inch bore and a 4-inch stroke. The cylinder casting and its integral head are of heat-treated gray iron, and the heat-treated, ground piston is fitted with three rings and a hollow steel wrist pin. An I-beam section of chrome-vanadium steel, fitted at both ends with phosphor-bronze bushings, serves as the connecting rod. Separate camshafts for the intake and exhaust valves are driven by gears in the magneto drive train. The overhead intake valve is of nickel steel; and the exhaust valve has a cast-iron head and a nickel-steel stem. The crankcase is of polished aluminum, and the hardened, tool-steel crankshaft is mounted in the crankcase on phosphor-bronze bearings. The crankcase has an oil-drain plug and an overflow pipe.
Ignition is effected by a Bosch high-tension magneto with spark plug, and the fuel is vaporized by a constant-level, float-equipped Schebler carburetor. A priming petcock is in the left side of the cylinder head. A compartmented tank, with one section for gasoline and the other for oil, is mounted at the upper bars of the frame, above the engine. On top of each compartment of the tank are a filler cap and a shut-off metering valve. The oil for the engine passes by gravity through a sight glass into the crankcase.
The spark timing is controlled by twisting the grip of the left handlebar, and the throttle, by twisting the right grip. The loop-type frame of brazed tubing forms a cradle that supports and protects the motor. The handlebars are tubular, arid the steering fork is fitted with both main and recoil springs. A narrow, metal toolbox is mounted vertically on the frame below the saddle, and the curved exhaust pipe culminates in a muffler below the toolbox. The wheels, with wire spokes and metal rims, originally carried 28-by 2 1/2-inch clincher tires, but 28-by-3-inch tires (contributed by Harvey S. Firestone, Jr.) were installed when the motorcycle was restored in 1947.
The wheelbase is 57 inches. The drive is furnished by a double-reduction roller chain (covered by metal guards) that runs from a sprocket on the engine crankshaft to a sprocket at the hub of the rear wheel. The clutch, which is on the rear-wheel hub, is operated by means of a lever on the left side of the machine, and is engaged by moving the lever forward. A pedal-and-chain drive, on the right side, incorporates a New Departure coaster brake. With the rear wheel raised free by the stand and with the clutch engaged, the pedals are used to crank the motor.
The brake is engaged by a slight backward pressure on the pedals. The pedals are not driven by the forward motion of the machine, but can be used for propulsion in an emergency, in which case the clutch is disengaged.
