Ariel Owners Motorcycle Club

I have a magneto of unknown origin that I have re-built but there is no spark at the HT lead. There is a spark (discharge?) at the points and a continuity test of the armature windings looks good. The earth plug and its carbon brush are new as is the HT lead and slip ring connector. The points are new and the armature has new bearings and rotates smoothly with no appreciable end-float. The HT lead connector carbon pickup to the slip ring is showing signs of rubbing on the slip ring (brass colour on the end) so I think it is making contact and I did swap the HT lead holder for one from a working magneto but to no good effect.

I have run out of ideas so any suggestions for tests or remedies are welcome.
Dennis

hi have you cleaned the slip ring or has it got damp or wet , i have took my mag off to dry it out after the bike was sitting out in the rain cold and damp under a cover for over a year after me having a big op and it stop sparking and now after keeping it in dry and warm over christmas and it is now sparking again

A photo or two of the mag will give some idea of what we're dealing with.

Usually sparking at the points happens because the condenser has failed.

However, another thought is that there is no connection between the spark
plug end of the HT lead and the HT windings in the armature. I don't remember
ever trying it so I have no idea what value to expect but i wouldn't expect a high
resistance. I'll find a mag that works tomorrow and measure the resistance.

Hello Dennis,
Have you looked through Brightspark's magneto maintenance and troubleshooting page? If not, it might give you some ideas:
http://www.brightsparkmagnetos.com/DIY/index.htm

An inoperative condenser or an open circuit in the secondary windings causes sparking at the points Eliminate the pick up and lead by checking the spark straight off the slip ring to magneto body. Nev

Thanks all for your helpful suggestions. I will try a few things and report back. I have bought a new slip ring but it won't arrive until mid-January. I am not sure that the windings to slip ring connection is sound as the hole in the slip ring looks worn. I should have mentioned that the mag is a Lucas MO1L but the information plate was been removed before I got it.
Dennis