ORIGINAL: Sport_Pilot
ORIGINAL: Motorboy
Flyboy Dave are right..
We has same system of the impulse coupler in the magneto mounted at the marine engine, when the engine are handcranked to starting the engine, it is to prevent backfiring and damaging arm/hands since impulse coupler will rotate magneto fast and ignite after TDC, it make easier handstart the marine engine.
Jens Eirik
If it rotates the magneto fast then it doesn't have to be turned over fast at all. In other words it is doing more than retarding the ignition. That is why it makes it easier to handstart.
In the impulse coupler are there a spring who are twisted first via timing gear in the engine before the impulse coupler are activated after TDC then the spring are rotating the anchor (rotor with coil inbuilded in the magneto) to make more energy in coil to give spark in the sparkplug while the engine are hand started. After the engine are started, the impulse coupler are deactived by centrifugal force (weights inside the impulse coupler) and the ignition timing are advanced.
Jens Eirik