energytransfermagnetobyhoytmckagen

8/14/2019 EnergyTransferMagnetobyHoytMcKagen

1/3

Energy Transfer Magneto

- Hoyt McKagen

Energy Transfer Magneto is easily made from standard alternator as used on mostearlier model Hondas of all sizes. Alternator is a six pole, split coil arrangementwith a perma-magnet button rotor. There are differences in the design among models

and year, but all are

suitable for

conversion. Many ofthese will swap

between motors, but

since individual unitsare wound respective

to demands of the

number of sparkcoils, the number of

cylinders/coils should

be the same.

ETM is wired so eachcoil primary has a

stator coil, set of

points and capacitor.Each of these

components has two

connections, one ofthem usuallygrounded as mounted.

To complete ETM

wiring, any remainingground connections

are made, and

components areconnected together at

the other ends, that

best being done by one primary lead from each stator coil pathed thru points, cap

and coil in their usual mounted positions. The primary may have sockets spliced intoit at various places to facilitate connections. This same lead can be extended to the

kill switch; for twins and multis that can operate by connecting the involved stator

coils together. Usually spark coils, points and caps can all be stock components asused with the original cycle, and mix and match is often successful. I've got a

CB360 barking with Yam coils from a CDI model Triple coils and in general, CDI

coils often give slightly better results.


2/3

Alternator coils are in two sets distinguished by

wire size and number of turns. As shown, there

are four lighting and two iggie coils. On thestator, the iggie coils are opposite each other and

so are pairs of lighting coils. The two lighter-gauge iggie coils are wired in series and are connected to brown or pink commonlead, along with one end of the lighting set. On single-coil setups (thumpers and 360

twins), the iggie coils can be used as wired, with the brown lead grounded and the

yellow lead from iggie coils used for the primary lead. On twin-coil setups (180

twins and multis) the iggie coils must be separated at one end from common and anextra primary lead brought out from the disconnected end. Somewhere between

these two coils their connection must be isolated, spliced to a wire and lug, and

grounded to a stator mounting bolt.

Battery/coil systems flow current thru coil when points are closed, building

magnetic field around primary to saturation. When points open, current stopsflowing and magnetic field collapses. Energy contained in field excites voltage flow

in both coils, generating spark voltage in secondary. Primary coil and capacitor forma resonant circuit that also feeds energy into secondary coil, prolonging spark and

probably accounting for spark 'ringing'. Battery/coil system thus has two

instantaneous sources powering the spark.

ET magneto operates in essentially the same way except for the stator coil subbingfor the battery, hence the similarity in the wiring. However, the magneto has an extra

instantaneous source: there is energy stored in the magnetic field at the rotor/stator

interface that is also available to the spark as the points open. A battery cannot

supply that kind of pulse! But stator coil also can't give continuous power, so pointsmust open and spark be produced when it's giving its best. Usually, the magnetic

pulse isn't wide enough to give you the full original range of advance, so it may belimited to about ten degrees or so (by brazing blobs onto the advancer stops) or

advance simply be done away with. I do the latter and find it has no effect on

performance nor if well tuned are they tougher to fire up.

Usually the desired pulse isn't where keyway places the stator. Often when settingthese up a specific procedure is helpful: Wire and connect the ET setup and lock out

or limit the advance mechanism. For timing purposes, temporarily lock in full

advance. It's helpful to loosen the valve adjuster screws, to keep spring pressure

from moving the motor; indeed one can also set these so the motor will stay in thedesired place. Remove the rotor and replace it on key, loosely secured. Time the

points to the appropriate full advance mark(s) on the rotor ... get it dead on using a

meter or continuity checker to verify opening point. Take the rotor back off andremove key. Place rotor at the point of optimum pulse and secure it moderately hard,

for testing spark. The key is not needed to make this a secure joint.

Optimum pulse we would expect to be at the point where the rotor and stator poles


3/3

have overlapped perfectly, where magnetic interaction is strongest. However, a real

magneto as found on tractor and Harley usually has the points open at some point

previous to that. The practical reason is, we don't want the spark to be fired as thefield strength is instantaneously beginning to decline. We want a robust increase in

magnetic field interaction to be going on at the rotor/stator as points open, becausethat means energy will continue to be fed to the spark and even at increasing rate. Infact, the spark continues over about the same angular distance that one pole initially

lags the other. So I advise the optimum point be with about 80% pole engagement

and correspondingly more if you run some auto-advance.

Make sure points are clean, as magneto performance depends on passing theheaviest possible current thru them. If points are clean and it's wired right it should

make spark while turning it over with a wrench. Some degree of tuning is available

by putting rotor in different relative positions on crank. After spark intensity is thus

optimized, torque rotor down and carefully transfer the timing from the points

opening position(s) back to the rotor for your reference marks for next time youwork on iggie.

energytransfermagnetobyhoytmckagen

Documents