EIC Magneto intermittent failure?

[Whit]

Has any one any ideas / suggestions on the following
1925 TS will start and run for 20 seconds approx then dies and wont start again for an extended period (15minutes or longer) and then runs again for 20 seconds or so.
I dont think it is fuel as the float level stays constant when it is running.
With the plugs out and shorted to motor I see a good spark on each AT TIMES but at other times nothing.
I have cleaned carbon brushes and slip ring. Does anyone have a recommendation for a modern spark plug for this model. This one is still fitted with the original mica insulated type, although I have been testing spark with modern plugs as well as originals.
I've owned this bike for 30 years and when I last used it about 20 years ago the problem did not exist.
Any Ideas?
Rob.

[Ken Rogers]

Hi had the same problem on my 26 EW ,a new slip ring in the mag cured it but there didn't look like there was anything wrong with the old one.

[Whit]

Thanks Ken. This ring looks OK also, looking thru the brush holder hole.
where did you get your replacement slip ring? Are they available from LDMCC spares?
Rob. Whit.

[Ken Rogers]

Hi got it at a local magneto guy in Newcastle,North East Magnetos,It only showed up faulty when he ran it up on his test rig.

[douglas1947]

Hi Rob,

could be the condenser. It wears by the time and could replaced, but it is inside the armature. So a test is a good idea.

Michael