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[Dennis C]

Further thoughts, you say you had the spark plug at makers setting?, this is far too big, set it to the correct 18thou and see how it goes, if all OK problem sorted, I have incorrectly been referring to the armature, it is of course in this case a rotor (thanks Revband), I have also had good service from, Paul Wolf Magneto & Dynamo Repairs 0117 9836702 or 07831446958, in Bristol, he re magnetised an M01 for me last year I think it was about £15.00.

[Adrian]

I remember being advised 20 thou gap for magneto and 25 thou for coil, som 18 thou sounds pretty close, especially if Tim is recommending 15 thou for helping a fading mag to work.



This old chestnut has come up elsewhere recently (though I don't remember seeing any mention in this thread), so please forgive me if it's not relevant to your Bullet, but I take it you're not using a resistor spark plug with a suppressor spark plug cap?



A.

[Dennis C]

Yes Adrian you are correct about the resistor's, non should be used with a magneto I perhaps incorrectly thought Chris would know this, most makers at the time advised a plug gap of 18-20 thou 20 being the maximum gap, as the gap gets wider with use it's best to go for 18 thou.

[Chris Tindal]

The gap is 15 thou and it's made an appreciable difference. I never gave the resistor spark plug/suppressor cap combination any thought. The cap is a red NGK supressor and the plug is an NGK B8ES, is this a resistor spark plug?

[Chris Tindal]

It seems the B8ES isn't a resistor type. I vaguely new Dennis but didn't give it any thought as I've not had a mag before. Should I be using a suppressor cap?

[Mark M]

Chris, no resistor or suppressor for a magneto. NGK make neat little black unsuppressed plug caps, usually found at garden machinery places or online. I just file off the letters NGK to divert the attention of the rivet counters!

REgards, Mark

[Chris Tindal]

Thanks Mark I'll get one and give it a go. I'll feel a little foolish if that's all it was.

[Dennis C]

Mark is correct do not use any type of resistor with the mag, this includes the HT lead, only use a copper cored one, a suppressed plug cap is unlikely to be the cause of you trouble though, the resistor holds back the spark and a higher voltage is required before the plug sparks, this is not good for the mag and can cause it to spark internally.

[Chris Tindal]

I do think the mag will be due a service anyway Dennis, I doubt it's had any tlc. The bike was a rusty pile of bits for decades before the previous owner threw it together without checking anything or spending anything on it apart from cosmetics. Anyway, come next spring it should be spot on

[Presto]

This thread is a bit of a mystery to me. I can’t see how any of the changes made – or suggested – could have resolved such a weird 30 min starting ritual!