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"A zephyr has 4 cylinders 2 coils which means 1 coil has to fire 2 plugs/cylinders at same time but one is one piston is in the tdc position and one in the bottom dead center. Since their is 2 coils on a zephyr 4 cylinders more than likely 2 lobes they alternate all that and don’t need the bakelite contraptaction you have in your flywheel"
I believe I made a mistake here in this statement. It should have been when 1 coil fires it fires 2 cylinders at the same time. Since their are 4 pistons 2 are at TDC at the same time and 2 are at BDC so it fires the 2 at TDC. Sorry for getting that part wrong but 1 coil is firing 2 cylinders at TDC at the same time.
On my 40hp Yamaha (CDI Ignition) outboard I rebuilt last year 1 coil fires both cylinders also. It is called wasted spark so both plugs fire the same time everytime. 1 piston is at TDC and one is at BDC. I sheered a flywheel key last year and the flywheel had slipped to right at 180 degrees from where it should be but it would still run just not correct. Took me forever to figure out it was a flywheel key.
I think your motor has no reed valves? and an unusual way of getting fuel (rotary valve) I think thats why it has the brushes are used to kill spark to the cylinder that doesn’t need it because piston is at BDC and fuel fumes are present. I think the zephyr also uses a rotary valve I have 3 of them and love them.
Did you ever determine what size condenser/capacitor value to use? Most the 1940 OMC smaller engines like the zephyr on the chart are showing .09 to .125 I wonder if by having less capacitance would that possibly help the situation?? Your using .2 just wondering by going down to .09 which would be half if that might somehow weaken the spark and allow the brushes to work better? You may still want to see if both plug wires fire with the Stevens Meter hooked up to coil and 1 not grounded with the .2 I suspect they will.
hope that helps,
Joe
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