Page 47 in the owners manual gives the timing as 36 degrees before TDC, fully advanced. (Be aware that fully advanced on the Mark series means with a tight cable).
The easiest way to set the mag is to remove the advance/retard cable and return spring so that the points cam can be set to the advanced position (clockwise looking at the points). Remove the L.H. HT pickup and turn the armature until you can see the brass segment on the slipring. Adjust the position of the armature so that the points are just about to open. With the R.H. rocker cover removed, turn the crank to TDC with the valves just 'rocking' on the R.H. cylinder. If you are working on a fully assembled engine, remove the spark plug and check the distance to the piston, then turn the crank backwards (clockwise, looking at the flywheel) and bring it toward TDC again - stopping when the distance to the piston is 7mm greater than before (this equates to 36 degrees before TDC). Then refit the mag and double check that the points are just beginning to open. Refit the cable and rocker cover, etc.
If the drive pinion has not been disturbed, you should be able to get the timing reasonably accurate by this method - bearing in mind that the advance/retard is there for making adjustments while riding. If there is any doubt, err on the advanced side, as this can be rectified with the control - running retarded will result in an overworked and overheated engine.
Regards,
Eddie.
