293 Four Square Drive Mount Pleasant, Michigan 48858
The following is the confession of a neophyte old engine
enthusiast or, ‘How my Wico Model EK magneto and I survived the
first few weeks of our relationship.’ After talking with fellow
old engine enthusiasts, it appears I may have delved into the
critter more than many. Thus, I thought I would share my
experiences and information gathered during the ordeal.
When I purchased the engine it had some compression, no cracks
in the cylinder or water jacket, most of the parts were on it (I
suspect there is some great repository in the heavens for mufflers
and gas tanks), and the magneto made sparks albeit weak yellow
looking sparks. I understand from my experienced old engine friend
this was a pretty good find.
My first thought was to fabricate a temporary gas tank and see
if I could convert some gasoline into noise, but better judgment
prevailed and I started to clean and check components
thoroughly.
Alas, the magneto! Being a retired electrical engineer and one
who has toyed with gas and diesel engines over the years, I felt
confident the rather simple EK magneto would be operational in a
few hours. Boy, was I wrong! I now know that although the EK is not
a complicated device in principle, it is full of special and
exacting needsor should I say mandatory requirements.
Upon opening up the magneto I found it had suffered many
indignities, e.g. one breaker point was cracked, the cloth wrapping
around the coil was torn and frayed, old lamp cord had been
soldered to the coil primary wire ends and wrapped in an abundance
of plastic tape, and a tape laden condenser was stuffed in the
cavity above the coils.
The movable breaker point was not even locked in place. This
should be a piece of cakere place the points, re-solder new primary
leads and encase the joints in heat shrink tubing, install a new
condenser, and finally coat the coils with glyptal (the red
insulating varnish used by electric motor re-builders) and we
should see a nice eighth inch long blue spark, right? Wrong!
I went to see my friend Mike Zingery, owner and operator of
Roy’s Magneto in Mt. Pleasant, Michigan. Mike repairs hundreds
of magnetos, largely for oil field engines, tractors, stationary
engines, and he ‘does rebuild 50 to 60 Wico EKs a year.’ He
even has an original Wico EK magneto test machine.
Mike asked if I had checked the coils for shorted turns or open
winding(s). I uttered a sheepish ‘no.’ Mike said ‘if
you can get a 7mm spark jump with a primary coil current of 1.2
amps or less, you probably have a good coil. What this means is by
applying an interrupted variable DC voltage to the coil’s
primary windings while measuring the coil current, one can get a
good idea of the coil’s condition.
From the junk box I found an old set of tractor points (both
sides), a small 1200 rpm electric motor which I fitted with a cam
made from more gems from the junk box, a battery from my portable
electric drill, a small wire wound rheostat, and a multimeter
capable of measuring DC amps.
As I slowly increased the primary current, at 1.18 amps I got
the much wanted 7 mm spark jumpthe coils were good. That’s the
good news; the bad news is that on the engine the magneto
wasn’t producing the kind of spark needed to make my hit &
miss engine start and run well. Were the magnetos strong enough to
make a good spark?
In an old engine primer I read, it stated ‘Some instructions
manuals say the magnets should hold a ten pound weight.’ There
was no indication as to whether the weight should be applied
directly to the armature so as to pull the armature away from
stationary poles or should the ten pound force be applied to the
trip mechanism. My EK is a Type 3 magneto (Type 2 seems to be more
common) relies on ‘cocking’ the Wico part number 186 drive
spring to snap the armature and movable point away from the magnet
poles. The smaller, number 97 return spring, functions to reset the
armature on the magnet poles. Supporting the magneto body in a vise
and hanging weights on the armature, my magneto armature supported
the ten pound weight but tripped at seven pounds when the force was
applied to the magneto/valve rod. It appeared that the magnets in
the EK were strong enough to induce a good spark. But it
didn’t!
I remembered Mike saying that the armature must break away from
both pole faces at the same time and they must uniformly contact
each other; if not, a weak spark is the result. The tripping action
is so rapid that it is difficult to visually determine if one pole
is breaking the magnetic circuit before the other.
To check the armature pole faces for equal length, I removed the
armature, found a reasonably snug fitting arbor to slide into the
armature guide pin hole (the shank of a good
5/16 drill will suffice) and placed the arbor
in a vise. Having a magneto base dial indicator (the same could be
accomplished by any firm reference stop and a feeder gauge) I
rotated the armature pole faces on to the dial indicator.
Sure enough one pole extended more than 0.035 of an inch further
than the other. I disengaged the dial indicator and gave the
shorter arm a ‘calibrated rap’ with a one pound ball peen
hammer. Rechecking with the dial indicator showed several more
‘precision adjustments’ were accessory to bring the
armature faces within a few thousandths of an inch of each other.
My EK was still weak.
The next move was to examine the armature/stationary pole match
up. After cleaning, careful examination in front of a good light, I
found the poles to be touching on the back side, but a considerable
gap existed on the front side. In fact, I could slide a 0.006 inch
thick feeler gauge almost halfway between the poles.
The proper repair approach would probably employ a surface
grinder to reface the armature poles, but I no longer have access
to such. The question became, did I still have the touch to
properly square these pole faces with a ‘Swedish mill’
(hand file) or should I try to rig up a grinding device in my drill
press? Oh, go for it! I coated the pole faces with the die maker
layout fluid (a magic marker will do just fine) and started to
file, checking where the metal was being removed and the clearance
with a feeler gauge frequently. I had to achieve a flat and square
surface.
After several nervous tries, I could barely start a 0.002′
feeler gauge under one corner that’s good enough. A re-check of
how much weight the armature would now support indicated an
increase of almost eight pounds and now the magneto would give a
spark almost every trip why almost every trip?
The Type 3 and the Type 1 EK magneto (the Type 2 has a different
spring and mechanical finger trip arrangement) relies on the
attraction of the magnet poles to the armature to allow the engine
cam to compress the number 186 spring to the point when it trips,
it snaps the armature from the magnet pole faces. This snapping
action is mandatory for a suitable current to be induced into the
primary winding.
I went looking for friction as a possible robber of the
spring’s stored energy and something that might slow down the
armature’s movement. I found the rod that activates the magneto
and the exhaust valve was bent and dragging on the rocker arm. Not
only did it have a bend, it had two ‘s’ shaped kinks in it.
I straightened the rod the best I could but resorted to buying a
piece of 3/8 inch steel rod threading
one end and hardening the end that contacts the exhaust valve
rocker arm.
Now I got spark every trip, but still a weak spark. I learned as
a kid while working in my uncle’s auto repair garage that a
yellow spark was not a ‘hot’ spark and what we want is a
blue spark. How accurate this rule-of-thumb is I cannot attest, but
it seems to apply.
I went back to Mike and had him recharge the magnets. A
subsequent magnet pull test proved the magneto would now support
slightly more than 30 pounds of pull weight, and most importantly,
I got a 3/16 inch long (the gap on my test
spark plug) blue spark every trip of the EK!
In summary, I can’t say that your EK must satisfy all the
criterion I forced mine to do. For example, I cannot say for
certain that magnets supporting a ten pound pull test will not
provide a good hot spark. My EK seemed to want a much stronger
magnet. Perhaps some more experienced magneto person can improve on
what I have reported. In any event, if you decide to work on your
ailing EK I hope the foregoing will be of some help.
