The New Star Motor-Bicycle

An exceptionally interesting self-contained power unit of practical and ingenious design. Leather-to-metal clutch on the engine shaft. Three speed gearbox. Chain drive.

The Star Cyc1e Co., although having hitherto held aloof from the motorcycle industry, will assuredly cause as much interest as any of the newcomers with the 4¼ hp. single-cylinder machine which they will stage for inspection at the forthcoming show, the essentials, viz., engine gearbox, clutch and carburettor, being of distinctly original design, and, moreover, fine pieces of work: apart from such points of distinctiveness, the whole of the power unit, comprising, in addition, the magneto and foot-starter, is capable of detachment from the machine en bloc, giving the model a note of originality and value as regards this point exceeded by none of its competitors.

Taking the engine, lubrication is forced to the main bearings by centrifugal action, the oil entry being via magneto chain case and timing case into a circular flanged ring, cast on the off side flywheel, and receiving oil from a guide web, cast integral with the crankcase, on its inner wall, a hole being drilled through the timing case at this point; centrifugal action delivers oil thence through the drilled crank pin to the big end and through the drilled connecting rod, which is a steel forging, to the small end, being finally driven through the hollow gudgeon pin to the cylinder walls, every part being thus well supplied from the sight drip feed oiler on the tank.

The cylinder head and valve chambers form a separate casting, bolted down to the cylinder by four holding bolts, and is a clean piece of work, the cooling fins being wide and thin, and the valve ports large. The valves are 1⅞ in. diameter, necessitating but about ½ in. lift, and the forward holding-down bolts can be swung forward for drawing the cylinder clear of the piston without removing the engine from the frame.

Timing side of the Star engine, showing    the foot starter and valve shield.

Valves are enclosed in an oil-tight aluminium cover, and the piston is provided with a stiffening flange round its base, while ball bearings are fitted to the clutch side of the main shaft, in addition to the plain bronze bush which is provided on both sides. The timing gear is exceedingly neat and strong, only one reduction wheel being employed, the three cams, exhaust, inlet and decompression, being cut from the solid, and on one spindle, which is mounted on Hoffman bearings. The decompressor is among the neatest we have inspected, calling for a minimum of space, an extension arm of the exhaust lifter carrying a small slipper lever rocker, which, under slight operation of valve lifter, is rotated into position between the exhaust rocker arm and decompressor cam, slightly lifting the valve at the end of the compression stroke. Further operation of the exhaust lifter automatically takes the work off its shoulders, so to speak.

Very heavy flywheels of 10 in. diameter are fitted, and the main bearings are most substantial. One of the beauties of the design permits the removal of the timing box and outer half of the magneto chain case without disturbing the mechanism in any degree, while the crankcase casting is formed to provide two platforms at the rear. Firstly, that to carry the magneto, and lower still, rearward, a second, which fits under the centre bracket, to which it is fastened by the four gearbox bolts passing through both members from the gearbox unit below, slotted holes allowing for ample adjustment. The crankcase lugs are arranged that the withdrawal of but three bolts allows the removal of the power plant complete.

The Star power plant which can be removed from the    frame, complete with gearbox, magneto and clutch.

The Star handlebar showing special dropped grips  with flats for taking control gear, and having four  concealed cables.

The clutch, again, strikes an original note, being of the cone type, leather to metal, and mounted on an outer extension of the engine shaft. It is cased-in, and oil-tight, and operated by a pedal at the extremity of the shaft, which is locked to a cam-faced ring that rotates thereon against a similarly-faced sleeve-end carrying the inner member of the clutch. Depression of the pedal thus thrusts the leather-covered cone out of engagement with the rotating outer member, which is fixed to the engine shaft. On the sleeve carrying the inner clutch member, a chain sprocket carries the drive to the gearbox, the countershaft of which is similarly fitted, and final drive is also by this means.

The gears are of the sliding type, with direct on top, operated through a sturdy lever, horizontally rotated, operating in a notched quadrant attached to the top tube. In fact, car practice is closely followed throughout the transmission, and a very sound job it is, an oil-bath chain case enclosing the drive from engine to countershaft, while a spring drive is incorporated in the chain wheel to absorb shock.

The carburettor is a new design multi-jet, and will probably be fitted as a two-lever for standard, although single-lever operation can be successfully employed. Three spray holes cover the jets, and over their faces slides the grooved throttle barrel, with a lateral motion, uncovering the holes in progression, the movement simultaneously opening up the hot air intake at the base.

An additional air lever operates a rotating sleeve segment between the throttle barrel and housing, thus giving further access to the hot air chamber, which is a further neat point in design. An aluminium collar casting, in two halves, embraces the upper radiating pins, and feeds, the carburettor with warm air; this should assist somewhat in cooling the engine.

Reverting to the gearbox for a moment, both shafts are mounted on ball bearings, and the gear wheels are of generous dimensions, while a large inspection door forms the rear side. A good foot-starter-pinion and segment is also fitted on the gear shaft in a convenient position. Bore and stroke are 89 mm. by 100 mm. and a desaxe setting has been adopted for the cylinder.

Valanced mudguards, with a hinged rear member for easy tyre repair, will be fitted, and needle valve petrol cocks for both carburettor and cylinder priming find a place on the tank.