Magneto fired ignition coil is not AC input, as being a single pulse transformer. It fires in milliseconds range. (not fast microseconds range of CDI) How to get the output increased in voltage?????? It is not AC output , and cannot use diode/capacitor multiplier like an AC transformer does. I tried a wound pulse transformer many ways that failed. If CDI was used with PF caps, which would work, the matching inductor for increasing to milliseconds range would be in high, unuseable Henry range inductance. STUMPTED!! The ignition coils are all autotransformers with 3 terminals, not 4 as regular transformers. The primary is connected to the secondary also. I need 8Kv changed to 24Kv. Regular inductive type ignitions only go to 15kv output. I also tried the added magnets to regular flywheel magnet ,to attempt getting a higher voltage going into primary by stronger magnetic field.. What about adding small inductor as back EMF as forward ?

 

What kind of engine is it? Most magnetos are a bit more involved than just a magneto and any attempts to alter the circuit are going to damage the internal circuitry. What do you think you need the higher voltage for?

 

There's not likely much you can do to increase the output of a magneto.
What's the purpose of getting more voltage, as it should be sufficient to fire a sparkplug.?

 

A typical magneto, as on an older single cylinder engine, is not even a transformer, but rather a single-pole generator. The way to increase the voltage is to reduce the air gap between the magnet in the flywheel and the magneto core that is close to the flywheel.
If it happens to be a much newer magneto that uses a set of breaker points, then to increase the output be sure that the breaker points are clean, and possibly replace the capacitor, often called the condenser.
I did experiment with adjusting the ignition system on a 1938 single cylinder engine at a farm many years ago. The breaker points system was on a rotary lawn-mower engine much newer than the antique one.

 

The only way to increase the high volts of lawnmower Magnetron ignition coil, is to bolt on another piece of laminations with a wire coil. The output of 1st secondary will be added to the next coil as an extension. The same magnetic flux is there, same time. There are differences in ignitions of the past . Some have higher secondary Henry inductance and ohms resistance, meaning there would be slightly higher output ignition volts. It is way less costly to experiment with small engines , but they need 24kv minimum for plasma path for amperage to pass, and must be in milliseconds time, not microseconds as in C D I.
A much more involved method is a second, opposite pole magnet put on flywheel next to other one with an opposite balancing lead weight. The dual magnetos would make AC into primary of the "old" style plain transformer type ignition . The secondary side AC generated could then use the diode and capacitor voltage doubler. The STENS brand aftermarket trigger modules work with either polarity ignitions. 2 blocking diodes would also be needed.
A man on You tube video tests his Biggs Magnetrons coils on bench with AC activated coils on old shaver laminations mounted next to the ignition laminations. The transposing magnetic flux runs the main ignition coil for spark. (trigger not tested)

 

Why do You want to increase the maximum Peak-Voltage ???

The Spark-Plug-Gap and the Compression-Ratio of the Engine will dictate the Spark-Gap-Voltage.

If You want a longer Spark-Duration, You will have to provide more POWER and add Resistance.

The stock Ignition-Coil provides plenty of Power, actually quite a bit more than is needed,
unless You are radically modifying the Engine.
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Actually, the way to get a lot more spark voltage is to use an external MARK 10 CDI module. with a regular ignition coil, at least 50 kilovolts. WITH THE FULL 12 VOLT BATTERY, more like 60 to 75 KV.
and a very fast rise time.