cylinder, it gradually effects a reduction in the amount of energy available for transfer to the ignition coil. This
reduction in spark energy will cause misfiring to occur, which in the event of the rider omitting to return the ignition
key from position " EMG " to " IGN ", serves as a reminder to do so. The contact points will be badly burnt if the
rider prolongs running in the " EMG " position.
Another feature of the system is that coil No. 2 eventually comes into operation during emergency
starting, so that after a few seconds of running on one cylinder, number two cylinder cuts-in and the engine
functions as a normal twin-cylinder unit. The fact that it will operate on both cylinders after a few seconds does
not detract from the statement, made in the previous paragraph, about the rising battery voltage causing
misfiring to occur.
Although the No. 2 coil " SW " terminal is linked to the same feed cable as the " SW " terminal of No. 1 coil,
it does not pass any of the energy transferred from the alternator, during the " energy transfer " pulse, as at this
particular instant the No. 2 contact-breaker points are open, open-circuiting the No. 2 coil primary circuit. It is
fed eventually, however, because the battery voltage or potential difference builds up due to the current from the
alternator passing through it, causing the battery to assume a stronger polarity characteristic. Therefore, in
between the No. 1 coil being fed by energy pulses from the alternator, the No. 2 coil will, when its associated
contacts close, receive current direct from the battery which is gradually becoming charged. This results in the
engine firing on both cylinders. It will not run at full power until switched to the " IGN " position, because the
energy now available for the No. 1 coil is being reduced and misfiring will still occur.
Actually, during the stage when both coils are functioning, their primary windings are being fed in
opposite directions. The No. 1 coil is receiving pulses from the alternator, via the battery, the insulated side of
the circuit, through the primary from " SW " to " CB " and back to the alternator. The No. 2 coil is fed by a
steady current direct from the battery, via earth, through No. 2 contacts to " CB ", through primary to " SW "
and back to battery-VE.
FAULTS WHICH CAN AFFECT EMERGENCY STARTING PERFORMANCE
In the foregoing description of the functions of the emergency start circuit, it was stated that the
energy transfer efficiency was high. It should give a starting performance, at " kick-start " speeds, equivalent
to that of a conventional type of magneto. Provided, of course, the circuit connections and units are maintained in
a good condition. If they are not attended to regularly and are allowed to deteriorate, then even emergency starting
becomes hard work and its inherent advantages nullified. Any of the following faults can affect emergency starting
performance, and they are the most likely to be encountered during normal service life.
Incorrect timing of the engine.
Faulty circuit connections.
Dirty contacts or incorrect contact gap setting.
Dirty plug or incorrect gap setting. Faulty
rectifier.
Dirty or corroded battery terminals.
Sulphated battery.
Incorrect Timing of the Engine
It is very important that care is taken when timing, for ignition purposes, any machine which is fitted with
an ignition system utilising " energy transfer " principles for emergency starting. To obtain the best possible
performance it must be accurately set. Remember, it is not only the piston/spark timing relationship which is
involved but also the " magneto " performance (spark energy) of the alternator.
This will be appreciated more fully when it is remembered that, as the rotor of the alternator is
keyed to the engine crankshaft, which in turn is coupled through the connecting rod to the piston, any movement
of the piston during the timing procedure will affect the position of the crankshaft and hence the magnetic timing
position of the rotor.
Summary of Contents for TW2
Page 1: ......
Page 55: ...SERVICE SHEET No 1050 contd Wiring Diagram 6 Volt Model...
Page 57: ......
Page 58: ...i SERVICE SHEET No 1050 contd...
Page 61: ......
Page 66: ......
Page 73: ......
Page 74: ......
Page 75: ......
