Thank you both for your helpful and educational answers.
H.
If the dwell and timing were originally correct on a points system, resetting the dwell after points wear or replacement should restore the correct ignition timing. However, most electronic systems don't have any wearing parts so the dwell shouldn't change.
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*Beauty is in the eye of the beer holder *Dave Plowman snipped-for-privacy@davenoise.co.uk London SW To e-mail, change noise into sound.