On the Racing Camshaft Models, an Amal Racing Carburettor with Twin Fuel
feeds is fitted. When tuning this for speed work select the main jet size which gives maximum
power and speed with the Air and throttle full open. The correct size is readily found by
moving the air lever at full Throttle openings : any increase in power obtained by half closing
the air lever indicates that the jet size is too small. Loss of power on closing the Air Lever
slightly shows that the main jet is rather too large. It is far belter to err on the rich side with
Carburettor settings. Weakness " Cooks " Sparking Plugs and other Engine parts.
Idling or slow running is governed by a knurled screw on the side of the Carburettor;
for Petrol Benzol it should be unscrewed about two and a half turns, but for Discol R.D.1
fuel, only about half a turn. Always adjust this control so that a clean pick-up and good
acceleration are obtained. From one eighth to three quarter throttle is governed by the
throttle cut-away; this is indicated in the way explained previously. Three quarter to full
Throttle is governed by main jet size.
LUCAS MAGNETO AND MAGDYNO LIGHTING SET
When Camshaft Models are not fitted with Magdyno Lighting a Lucas Racing
Magneto is fitted. Magnetos have now reached such a stage of perfection that trouble is
seldom if ever experienced with these. Their condition, however, does affect the performance
of the machine considerably. If any trouble is experienced with the Magneto this will usually
be traced to either the High Tension pick-up or the contact breaker. Should starting become
difficult and Ignition is suspected, inspect the following points, remove sparking plug, hold
this against the cylinder with the high tension lead attached to the terminal and kick the
Engine over (be careful to see that the hand is nowhere near the terminal, and that the plug
body makes contact with the cylinder or a shock will be felt) if there is no spark at the points,
take the terminal away from the plug and hold this about 1/8- in. from the Cylinder, at the same
time kicking the Engine over; if a spark is now visible the fault is in the Sparking Plug. Check
off the gap between the points, this should be 20 Thou and if necessary adjust them by either
tapping the electrodes together or springing the outside electrode away with a thin screw-
driver. If the plug still refuses to spark, unscrew the centre from the plug body and clean
the mica insulation with a Petrol soaked rag. Make sure when assembling the plug that the
gap between the points is correct. Should it be impossible to obtain a spark from the High
Tension Terminal against the Cylinder, first remove the High Tension Pick-up and examine
this; if any carbon or dust exists wipe this away, also take a pencil or similar object, cover
this with a cloth and insert into the hole left by the removal of the Pick-up, press this lightly
on to the Slip ring, and to remove any carbon which exists rotate the Engine with the Kick
Starter.
Should this not have the desired effect turn to the contact breaker, A Spanner is
provided in the tool kit for adjusting the contact breaker points and removing the contact
breaker centre pin. Take the Contact breaker out bodily by first unscrewing the Contact
breaker Centre Pin and Rocking the Pin from side to side in the centre of the Contact Breaker,
it will then leave the taper hole in the Armature shaft. Now that the Contact Breaker is free
turn the Rocker Arm locating spring and prise the Rocker Arm off its Pin; the Points will then
be visible. If these are pitted or show indications of scaling, file the surfaces of both evenly
with a smooth file, afterwards smooth with fine emery cloth.
When replacing the Rocker Arm on its Pin see that this is an easy fit; a tittle grease
should be smeared round the pin. Be careful when re-fitting the contact breaker to see
that the keyway on the taper of the contact breaker body locates properly in the Armature
shaft before tightening the Centre Pin.
A Gauge is provided on the side of the Contact Breaker spanner for checking the
gap between the points.
Lucas Magdyno.
—The previous information covering the Lucas Magneto applies
also to the Magneto Portion of the Magdyno. The Dynamo portion of the instrument is
detachable and can be removed in the following manner :—
—16—
www.ajs-matchless.info
