Why Would Spark Ignition Need Rectification?

Automotive engine spark is switched either by HV contacts (a distributor) which needs regular maintenance (rotor and distributor cap replacement) or by multiple coils. You can run a four-cylinder engine on four coils, or two coils with polarity-switching diodes, or one coil and a maintenance nuisance.

For an inline 4 with 2 coils, car or motorcycle there's no polarity switching diodes - usually the pickup coil flips a bistable to & fro to drive the LT circuit switching transistors.

Its called the; "wasted spark" system, as each coil has 2 leads - one fires its cylinder just before TDC, the other fires its cylinder while the valves are "on the rock".

Only if its a 0 -360 deg twin (pistons go up & down together) - certainly a lot of 2-cyl motorcycles are 0 -180 deg twins.

no fancy diodes are needed

Actually polarity does make a difference - the centre electrode runs hotter than the side electrode, therefore the centre electrode parts with electrons more easily.

You can get the spark to jump the gap at a lower voltage if you make the centre electrode negative.

If you knew your basic theory the answer and the reason behind it would be glaringly obvious.

It has two magneto / alternators, one for the ignition and the other for running lights/charge up a battery.

It's a simple low tension magneto ignition system and the shop probably confused it with an "energy transfer" ignition which is slightly different. Either that or they used a coil designed for the other system (an extra insulator).

Bret Cahill

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What leads does the original coil have?

Actually it _is_ an "energy transfer" -- on of the dumbest names of all time -- system and they had the wiring correct.

The problem was the kill switch. They ignored that and instead swapped out the good old discontinued coil which steps up 3 - 4 orders of magnitude for a CDI coil which only needs to step up 2 orders of magnitude.

The new coil puts out a spark but not enough to get anything on fire.

Is it common to rig two ignition coils together to get higher voltage?

They seem to have CDI conversion kits in motorcycles but not outboards.

Bret Cahill