After suffering an intermittent misfire for well over a year on my Enfield WD/CO and repeatedly stripping and cleaning the carb. Also I have had problems starting the bike recently. I seem to have traced the problem to this plasticy/papery thingy. It's an isolator that fits between the magneto drive end bearing and the body. It has started to break up and according to my mag man......they do do that sometimes.
Ron
email (option): ronpier@talk21.com
Jo'b
Let's keep this discussion on the machinery rather than getting personal, eh Jobby ?
Exactly so Douglas, and yes John the bearing was wobbly around like a dick in a bucket!
Not the easiest of mags to remove on a CO as the exhaust has to come off to remove the timing cover. Much easier on the Triumph I have been working on where you just have to remove one screwdriver slotted plug. Ron
email (option): ronpier@talk21.com
hi ron on early mags up to 1951 drive end bearing to small 12mm for engine power later mags used 13 mm bearing gasket with fingers impregnated with palm oil to stop tracking you will need a new mag body bill
Hello! Someone using my name and no punctuation? It's not me! The real Ron Pier
email (option): ronpier@talk21.com
I had that problem during the International BSA rally in Scotland YEARS ago. I replaced the paper with a piece of a coca cola tin and it took me home safe.
Henk
email (option): ahum@quicknet.nl
Is it still in there Henk?..
...Ian 
Failure of the points end bearing has more tendency to have an effect the points gap..In my experience the bike will start and run ok but as you hit 35-40mph it starts to misfire.
With your insulator washer broken up and the bearing loose in the housing on the drive end I think it may be more likely that you had an intermittent 'short' as the bearing outer contacted the mag body...Ian
Ian, this is where you are completely wrong, please re-read my earliest post, it does not matter when the bearing housing contacts the mag body, it is earthet anyway via the earth brush, on the side of the mag housing!
Cheers,
Lex
email (option): welbike@welbike.net
And yet Lex thinks that shouldn't be an issue? As you know Ian, mostly the bike was pulling like a train. But I had that misfire on fast tick over and sometimes it wouldn't start hot or cold
I'm reluctant to finish the job for fear of further stress and disappointment. I wish I'd never met Lex Ron
email (option): ronpier@talk21.com
Ron Ian,
My comments were purely for the technical aspects of how a magneto functions, and what the insulator washers are for, a basic understanding of these really helps sorting out faults.
Ron, your problem with the magneto might have an combination of tiny faults, but as I said before, the bearing touching the housing can't make any difference.
That there would be excessive play may have to do with it, but I suspect a faulty armature or condenser, or a too short points operating plunger, this greatly affects things.
Ps, I love you too
Lex
email (option): welbike@welbike.net
Thanks Lex. My mag man has bench tested the armature etc. and rebuilt the mag with new isolater washer and correct points gap. I am quite used to setting the timing on most bikes, but this CO is a right bugger. For a start you have to remove the exhaust to get the cover off. I must have nipped up and undone the pinnion nut 50 times to get the right setting The gap was either too big or then too tight. I had also previously lapped the gear onto the shaft but I got there in the end. I have no hankering to go through it again in the near future unless I have to.
I have recently attached a mag with a ring cam to a
bike and they are more fiddly, but I got that set after only about three attempts. Ron
email (option): ronpier@talk21.com
Your quite correct Alex..I got that one wrong. The insulator washers around the bearings were fitted to discourage earthing through the bearings which in itself would not affect the performance of the spark. Lucas fitted the insulators as they were concerned about the effects of 'arcing' in the bearing if the electricity took that path, leading to possible burning/etching of the bearing surfaces....Ian