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BSA B40 spark plug

evo boy

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Electronic ignition or not I think it has no major impact. Start with what is recommended for B40 trials riding.

You may find some answer here http://www.bsaotter.com

Think electrex is delivered with correct cap.

Remember that modern petrol doesn´t foul plug as much as before. Long time running may be necessary before reading plugs. If black colour after short time it might be oil contamination and it hasn´t much to do with spark plug grade, but oil taking part in the combustion process and it should generally be avoided.



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Rupert Ratio "Unit Single Manual" states for 1962 bikes.... N5. I would try a projected N11YC or even N12YC and see how it goes. Projected spark plugs must not bang into something (piston or valves) N5 is non projected as normal of that day. Think N5 would equal N9 projected, or just about. A plonking trials bike may need a little hotter plug. Do not replace original Electrex cap. It might sit there for a reason (suppression)

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