Instruction manual

TRANSMISSION SERVICE

THE GEAR BOX

The gear box provides four speeds and has a positive foot change, operated by the right

foot, and a kick-starter.

It is retained to the frame by being clamped between the two engine rear plates by two

bolts. The bottom fixing bolt acts as a pivot. The top fixing bolt passes through the

gear box top lug and the rear plates, which are slotted, thereby allowing a swinging fore

and aft movement of the gear box to enable the front driving chain to be adjusted. That

movement is controlled by a bolt that has an eye encircling the gear box top fixing bolt

and which passes through an eye block secured to the right-hand side engine rear plate.

Two nuts threaded on the eye bolt, one on each side of the eye block, provide means of

accurately tensioning the front chain and, after that adjustment, locking the eye bolt

in its required position.

The Spring Frame Competition machines are fitted with the B.A. type gear boxes.

These vary in detail (principally in respect to dimensions), from the gear boxes fitted to

all the other models, but the transmission of power through the gears and all the other

information given in this section is equally applicable.

TRANSMISSION OF POWER THROUGH THE GEARS

(See Illustration 16.)

First, or lowest, gear

Sliding gear (C) on mainshaft (T) is in mid-way position, i.e., disengaged from gears

B and D.

Layshaft sliding clutch (W) moves to right and engages with gear (G). Power passes

through clutch A, to mainshaft T, to mainshaft sliding gear C, to layshaft gear G, to

layshaft clutch V, to layshaft gear E, to main gear B, to chain sprocket J.

Second gear

Sliding gear (C), on mainshaft, is in mid-way position, i.e., disengaged from gears B and D.

Layshaft sliding clutch (W) moves to left and engages with gear (F).

Power passes through clutch A, to mainshaft T, to mainshaft sliding gear C, to layshaft

gear F, to layshaft clutch W, to layshaft V, to layshaft gear E, to main gear B, to chain

sprocket J.

Third gear

Sliding clutch (W), on layshaft, is in mid-way position, i.e., disengaged from gears F and G.

Mainshaft sliding gear (C) moves to right and engages with gear D.

Power passes through clutch A, to mainshaft T, to mainshaft sliding gear C, to mainshaft

gear D, to layshaft gear H, to layshaft V, to layshaft gear E, to main gear B, to chain

sprocket J.

Fourth, or top gear

Sliding clutch (W), on layshaft, is in mid-way position, i.e., disengaged from gears F and G.

Mainshaft sliding gear (C) moves to left and engages with main gear B.

Power passes through clutch A, to mainshaft T, to mainshaft sliding gear C, to main gear B,

to chain sprocket J.

NOTE—Clutch A is connected to the engine sprocket by the front driving chain and chain

sprocket J is connected to the rear wheel by the rear driving chain.