Brightspark Magnetos

Re-install the contact-breaker assembly, ensuring that it registers properly with the armature shaft. It should fit properly in only one precise position. While holding it in that position, tighten the centre screw, but do not use undue force. Then check that the contact-breaker assembly is not wobbly on the end of the shaft.

Ring cam versions:

• Rotate the armature and check that the contact- breaker spring never touches the cam.

  • With Lucas devices, the fixing hole at one end of the contact-breaker spring is slotted so that the effective length of the spring can be adjusted as necessary.

• Rotate the armature and check that, when the points are fully open, the moving point assembly is not fouling anything.

  • With Lucas devices, if it fouls the contact-breaker spring, the contact-breaker assembly will need to be removed and the effective length of the spring increased as necessary.

  • With BTH devices, if the moving point assembly fouls the eccentric pin, the pin will need to be adjusted.

Face cam versions:

• Rotate the armature and check that the contact-breaker assembly does not foul its housing.

• Housings can sometimes get misshapen, in which case try to rectify that.

• Also, some pattern contact-breaker assemblies are too large at the 'fat' end and need to be filed or ground to size.

With the points fully open, adjust the points gap to 0.012" (0.3 mm).

• Twin- and multi-cylinder magnetos:

  • The points gaps with the heel at the centre of each lobe of the cam should be the same, but a small difference is inconsequential.

  • If there is a difference, adjust the points so that it is the smaller gap that is 0.012" (0.3 mm).

Place a clean piece of strong paper between the points, and with the points closed pull the paper out. Check for any dirty marks on the paper. If there are any, repeat until the paper comes out clean.

Open the points and blow between them to dislodge any remnants of paper.