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An “idle” spark on a 4stroke has no measurable effect because there is no burnable mixture in the cylinder. Thus it has no effect on the engine and can simplify the timing train. It might be employed for example to save weight or for cost of manufacture.

A 2stroke on the other hand always has a burnable mixture somewhere about it. (Even if it is only the nearby air being lit by the rider’s language when the blighter won’t start…!) Therefore an idle spark on a 2stroke can serve no useful purpose and may even result in unpredictable misfires, I cannot imagine any reason why it could be of benefit. By and large I’d say it’s better not to go there.