Ignition (Section A); Lubrication; Adjustment; Contact Breaker With Cover Removed - BSA M20 Maintenance Manual And Instruction Book

IGNITION (Section A)

A(1) "MAGDYNO" TYPE M01
A(2) Magneto Routine Maintenance

Lubrication

The cam is lubricated by a wick, contained in the
contact breaker case, which must be given a few
drops of thin machine oil about every 2,000 miles.
To get at the wick, remove the spring arm (A, Fig. 47)
carrying the moving contact and withdraw the screw
(B) carrying the wick. At the same time after
Fig. 47. Contact breaker with cover removed.
unscrewing (H) remove contact breaker and take
from its housing (C) the tappet which operates the
contact breaker spring and lightly smear with thin
machine oil. When replacing the contact breaker
components, see that the small backing spring (D) is
fitted immediately under the adjusting screw (E) and
spring washer and that the bent portion faces
outwards.

Adjustment.

After dismantling the contact breaker in order to
lubricate, the contact setting should be checked.
Turn the engine until the contacts (F) are fully
opened and insert the gauge provided (.010" - .012"
thickness) between the contacts. If the setting is
correct, the gauge should be a sliding fit. If there is
an appreciable variation from the gauge, slacken the
locknut (G) and turn the contact screw by its hexagon
head, until the gap is set to the gauge. Tighten the
locknut after making the adjustment.
A(3) MAGNETO – Testing in position to locate
cause of misfiring or failure of ignition.
Disconnect the cable from the sparking plug and hold
the end about 1/8 " from some part of the cylinder
block while the engine is turned over. If the sparking
is strong and regular the fault lies in the sparking plug
which must be removed for examination and if
necessary cleaned and adjusted.
Next examine the high-tension cable. After long
service, it may have become cracked or perished and
the magneto may be sparking through the insulation
to a metal part of the engine or frame. Correct by
replacing the cable.
If the performance of the magneto is still
unsatisfactory, the contact breaker may require
cleaning or adjustment (see paragraph A (2)) or there
may be an internal fault in the magneto. The
following procedure should, therefore, be adopted.
A (4) Magneto Contact Breaker – Cleaning
Remove the contact breaker cover and examine the
contacts. If they are dirty, they must be cleaned by
polishing with a very fine carborundum stone or very
fine emery cloth; afterwards wipe away any dirt or
metal dust with a petrol moistened cloth. Cleaning of
the contacts is made easier if the spring arm carrying
the moving contact is removed as described in
paragraph A (2). Examine the spring arm of the
contact breaker and wipe away any rust.
Adjust as described in paragraph A (2).
A (5) H.T. Cable
Should be 7mm in diameter. Other sizes such as
5mm and 9mm will not fit in the immobiliser and
suppressor. The cable must be replaced if the
rubber insulation has perished or shows cracks and
becomes brittle. To fit the new cable to the pick-up
terminal (Fig. 48) thread the knurled moulded nut (A)
over the lead (B), bare the cable for about ¼ ", thread
the wire through the metal washer (C) removed from
the old cable and bend back the strands (D). Finally,
screw the nut into its terminal.
Fig. 48. Pick-up terminal.
A (6) Pick-up
Examine the pick-up or high tension terminal (A, Fig.
51). See that the carbon brush (B) moves freely in its
holder, being careful not to stretch the brush spring
unduly. While the pick-up is removed, clean the slip
ring track and flanges (D) by holding a soft cloth on
the ring while the engine is slowly turned by means of
the kickstart. When replacing the pick-up, do not
forget to fit the cork gasket (C).
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