Lea-Francis Motorcycles

Today in Motorcycle History

Lea-Francis Models for the 1920/1921 Season

Lea-Francis 3½ h.p. 1920

A solo mount of refinement, the 3½ M.A.G.-engined Lea-Francis.

Lea-Francis 5hp V-Twin 592cc

The new three-speed gear box fitted to the 5 h.p. model. On the 1921 Lea-Francis 5 h.p. machines this M.A.G. engine of 592 c.c. will be used.

Lea-Francis Gearbox Detail

The cam and one of the striking forks of the new Lea-Francis gear box.

A Lea-Francis Sidecar Outfit.

Two Three-speed Machines to be shown at Olympia. New Model has 5 h.p. M.A.G. Engine and New Type Gear Box.

LEA-FRANCIS motor cycles for some time past have been fitted with the 3½ h.p. M.A.G. engine and two-speed countershaft gears. This type has become so well-known and justly popular that it is hardly necessary to give a detailed description.

For 1921 only one outstanding feature has been changed, this alteration being the provision of an additional gear ratio. The new three-speed gear remains housed in the large circular bottom bracket, as was the case with the two-speed - in fact, externally it resembles an earlier type of three-speed box fitted to a few Lea-Francis machines. The details have, however, been redesigned and stiffened up, and the box has successfully withstood long distance road tests.

Smooth Gear Change.

One sliding member only is used, top and bottom ratios being engaged by dogs, while the middle gear wheels are made with heavier pitch teeth, so as to withstand the meshing of the wheels. An excellent feature of the gear is the easy "change," and on an experimental machine without the final "gate" we found that we could slip from top to bottom and bottom to top without noise or jar as the middle gear was passed.

A new carrier and the change-speed gate are the only visible signs of difference between the present two-speed and the new three-speed models, and the new machines retain all the well-known L.F. features, including finish.

An Enlarged Edition.

Quite a departure has been made by the Lea-Francis Co. in producing a sidecar machine. Although the general features follow the lines of existing L.-F. models, the 5 h.p. M.A.G. engine will be fitted, the magneto or Magdyno carried in front, and a three-speed gear box mounted on rearward extensions of the engine plates. The new gear box is of the constant mesh type, the two sliding members being controlled by the action of a cam through the medium of two striking forks. All the selecting mechanism is mounted above the box, and the whole is surmounted by a large and accessible oil filler.

A positive adjustment for the tension is provided, and as the kick-start is mounted on the clamping bracket an movement of the gear box leaves the starting quadrant in correct adjustment, most unusual and desirable feature is the fact that the multiplate clutch is mounted on the engine-shaft, in which position it possible to use either lighter plates or a lighter spring.

Aluminium Chain Cases.

Both the front and rear chain cases a of cast aluminium and particularly easy dismount. The rear chain is, of course brought over to the side remote from the sidecar, and by the use of a special cranked lug in the rear end of the chain stay, a sound chain case, split horizontal is rendered easy.

It is probable that 25in. x 3in. tyres will be fitted, and the machine should prove to be admirably adapted to sidecar work

It is yet too early to give details the new Lea Francis sidecar, though understand that it is to be in keeping with the motor cycle, and will be attached, course, to lugs incorporated in the frame of the machine.

The Motor Cycle November 11th, 1920. Page 554

5 h.p. Lea-Francis 1920

Plated parts have been avoided and every other consideration shown for the all-weather rider on the new 5 h.p. Lea-Francis.

5 h.p. Lea-Francis 1920

Valve side of new 5 h.p. Lea-Francis power unit, showing the new three-speed gearbox with enclosed selector mechanism.

The 1920 Olympia Show.

Lea-Francis. (Stand 58.)

  • 5 h.p.; 64x92 mm. (592 c.c.); twin-cylinder four-stroke; overhead inlet valves; hand pump lubrication; Amac carburetter; Lucas chain-driven Magdyno; three-speed constant mesh type gear; chain drive; 26x2½ in. tyres.

Lea and Francis, Ltd., Lower Ford Street, Coventry.

The Lea-Francis needs no introduction; for many years it has been regarded by many as one of the highest class machines on the road, albeit one of the most silent. Even at a first glance the machine looks most serviceable and workmanlike - in fact, it in many ways reminds one of car practice, so thoroughly has the detail been studied. The M.A.G. engine is chiefly interesting because the inlet valves, together with their rocking levers, are enclosed, while the exhaust valves have their stems and springs exposed. From the exhaust ports gas is led through flexible pipes to a very substantial silencer rigidly bolted below the frame, and of considerable size. On the 5 h.p. machines power for electric light is supplied by a Magdyno placed in front of the engine, and efficiently guarded from mud by a curiously shaped coverplate, which also acts as an additional protection for the rider's feet.

The 3½ h.p. machines are not provided with this fitting, but the magneto is placed behind the engine. As am example of the detail work, it may be mentioned that the high-tension wires are carried through in steel tubes on their way to the plugs. The dry plate clutch of the 5 h.p. model is on the crankshaft and in a substantial aluminium case, which encloses also the chain drive to the countershaft, and an inspection cover, very similar to the one on the contact-maker of the magneto, allows the tension of the chain to be judged. On both models the gear box is of very robust proportions, and the oil filler on the 5 h.p. three-speed model is of exceptional size. On the 3 ½ h.p. 64x77 mm. model, the clutch is on the countershaft, and the gear box is housed in a circular lug which forms the bottom bracket, but in the new 5 h.p. machine an aluminium box is mounted on extensions of the engine cradles.

Olympia Show, 1920
The Motor Cycle, December 2nd, 1920. Page 701