This blog, in addition to the usual maintenance details for classic mini cars, an attempt is made to explain the "whys" and "wherefores" of the various jobs.

Sunday, 11 October 2009

Servicing the Contact-breaker Points

Most instruction manuals dismiss the all-important subject of contact-breaker maintenance far too briefly. It cannot be too strongly emphasized, for example, that the gap between the contact-breaker points should never be measured with a feeler gauge unless the points have previously been trued-up with a fine carborundum stone or with very fine emery cloth. After only a few hundred miles of running a small "pip" forms on one point and a corresponding "crater" on the other, owing to the transference of microscopic particles of metal by the spark that occurs whenever the points open. The "pip" renders it impossible to obtain a correct reading with a feeler gauge.
On most models it is better to remove the radiator grille in order to make the distributor more accessible, although it is possible—but awk¬ward—to adjust, remove and refit the contact-breaker points by passing a long, slim screwdriver through the grille.

In any event, however, owing to the almost horizontal mounting and low position of the distributor it is preferable to remove it from the engine for servicing. To avoid upsetting the ignition timing, the bolt passing through the split clamp at the base of the distributor should not be slack¬ened. Instead, the two set-screws that secure the mounting flange to the crankcase should be removed. It will be necessary to remove the distri¬butor cap, disconnect the low-tension wire from the terminal on the side of the distributor and disconnect the pipe union at the vacuum-timing control, being careful not to twist the small-diameter pipeline. The distributor can be lifted away.
It will be seen that the projection on the driving coupling is offset, so that it will be impossible to replace the distributor with the rotor pointing in the wrong direction.