BTH Magneto

Important. Should it be necessary to alter the Ignition setting DO NOT ATTEMPT to loosen the nut securing the Automatic Timing-unit to the Magneto Armature before reading the instructions on page 57.

Preliminary Work. Remove the Contact-breaker Cover from the Magneto and rotate the Crankshaft with the Footstarter until the Contact-points are fully open.

Check the gap with the gauge on the Magneto Spanner, and if not correct reset the adjustable point to give the right clearance.

Fix a Timing Disc and Pointer (as described in the last section) after removing the Dynamo Belt-cover.

Open the Throttle and Air Controls fully.

Engage the Footstarter and rotate the Crankshaft until compression is felt in the Cylinder,

Release the Footstarter, and then remove the Sparking-plug.

Set the Piston to Top dead -centre and adjust the Pointer to zero on the Timing-disc (see previous section).

Move the Crankshaft BACK about 20°, and with the fingers separate the contact-points. Place between the Points a small strip of Cigarette paper or paper of similar thickness (.001 to .0015-in.).

Release the Points on to the paper.

Checking. Rotate the Crankshaft forward very slowly whilst maintaining a light pull on the Cigarette paper.

If the timing is correct, the grip of the Points on the paper will cease when the Crankshaft is between 4º and zero, or 12° if Premium grade fuel is always used.

If not correct loosen the Automatic Timing-unit from the Armature (see page 57) and reset it.

Should no Timing Disc be available the timing can be set to Top Dead Centre by checking by the Piston, but in no circumstances must the timing be set so that the spark occurs AFTER Top Dead Centre.

A Timing Disc can be made quite easily by marking out a card or metal disc in degrees by means of a Protractor.

Note.- The apparent lateness of the timing is because the Automatic Timing-unit is holding the Magneto into full retard. When the Engine is running the timing is automatically advanced the correct amount to suit the Engine speed.

Checking the Ignition Timing (Lucas Magneto).

The procedure is as above except that the timing is set so that the points separate 38° before top dead centre with the timer unit fully advanced - i.e., fully open.