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Old 12-01-2020, 06:28 PM   #14
nkaminar
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Join Date: Jan 2012
Location: Western North Carolina
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Default Re: Starter Mechanism

Impulse couplings, for those who don't know, have a spring inside that winds up against a stop. After a few degrees the stop lets go so that the spring makes the magneto spin fast enough to produce a hot spark. It also has the effect of delaying the spark so that it is not advanced. After the engine starts the coupling disables the stop so that the magneto has the normal advance. The stop is controlled by centrifugal force which increases with higher rpm.
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