Reply To: 1960 40 HP – Bottom cylinder misfire

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October 28, 2026 at 11:07 pm #330667
JOSEPH BRINCAT
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    I should have asked , have you checked the spark and timing using a timing strobe light? That motor should have the timing marks on the mag plate and corresponding marks on the flywheel. See if the timing remains consistent and steady on both cylinders up through the speed range. Referencing my previous post about the 9.5 hp ,, a dramatically fluctuating timing indication on the lower cylinder was the clue to diagnose the ultimate problem.

    Joe B