Engine/Primary Transmission

C

SECTION C38

IGNITION TIMING

Ignition timing can be checked and if necessary reset either with the engine stationary or, using a stroboscope, with the engine running. The stationary method is quite satisfactory where a stroboscope is not available. However, for greater accuracy, the stroboscope method is preferable,  since it also checks auto advance function.   A timing indicator plate is attached to the outer primary chaincase to align with the corresponding mark on the rotor, the marks being visible after removal of the chaincase inspection cap (see Fig. C47). The latest Lucas rotor has two timing markings opposite each other. Note that the presence of the surplus marking will not affect timing, either static or with a stroboscope. To explain - the engine must be running for a stroboscope to be used. Setting the timing by the wrong marking would mean the spark was timed at bottom dead centre and the engine would not run. If the engine is timed on the correct stroke, the stroboscope will not pick up the wrong marking. Similarly with static timing, only the correct marking will align with the calibrated scale in the primary case with the piston near top dead centre on the firing stroke for the cylinder being timed.

Ignition Timing Basic Procedure Prior to Checking
Straightforward assembly of the auto-advance mechanism and contact breaker assembly is covered in Section C31 as part of the Timing Cover reassembly procedure. It is however, necessary to locate the auto-advance cam approximately prior to timing. It is assumed that the auto-advance mechanism is loose assembled to the taper in the camshaft and that the contact breaker backplate screws are central in the adjustment slots. Remove the inlet rocker cover and the right hand exhaust rocker cover and both sparking plugs then turn the engine forwards on the kickstart until T.D.C. is located on the right cylinder with both valves closed at the firing position. Identify by wire colouring the contact breaker points for the right cylinder then turn the auto-advance cam until it just starts to open this set of points. Secure the cam with washer and centre bolt. The engine is now ready for accurate timing.
Ignition Timing Procedure - Engine Static
1	Remove both spark plugs.
2	Remove the inspection cap on the chaincase.
3	Remove the contact breaker cover.
4	Clean and adjust the contact breaker points as described in Section C40.
5	Remove the auto advance cam centre bolt.
6	Replace the washer from this bolt with the special washer 06.0949 having a hole large enough to clear the central portion of the unit and thus abut to the cam.
7	Replace the auto advance cam bolt with special washer, rotate the auto advance to the full advance position (it will rotate only one way), hold and tighten the bolt. The washer bearing against the cam will hold this in the full advance position.
8	Establish that the cylinder on which the timing is being checked has both valves closed at Top Dead Centre (T.D.C.) and rotate the engine forwards by engaging top gear and turning the rear wheel, until this is the case.
	The contact breaker points leads are black and yellow or black and white and this feature allows the operator to check which set of points are feeding which coil and cylinder. The factory standard arrangement is for the left coil and cylinder to be fed by the yellow/black rear set of points.

<<

<

rocbo.net

>