Lots of reasons to open the mags and spend a bit of money on
them.

Much good stuff snipped

Wow -- thanks, Dan. I didn't understand half of what you wrote, but I've
saved your post for the future day when I've got time to figure out things
like "electricity" and "engines"...

;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"
wrote in message
oups.com...
Talk to your A&P. Proceedure is specified in the Service Bulletin.
Mag(s) have to be removed, split, internally inspected (particularly
the impulse coupling), lubricated, both the E gap and points gap set,
new gaskets, reinstalled on the engine, and retimed.

The E-gap is determined by points gap; they're not separate
settings. The ideal is to set the E-gap, since wear to the points and
cam can result in the wrong E-gap if the adjustment is made using
points gap.
Most of my students struggle with the theory of the magneto's
operation, and I imagine most pilots are no better off. The E-gap is
the point at which the mag's rotor (a strong permanent magnet) is past
the neutral point after having generated a current in the primary
winding. This current generates its own field, which in beginning to
collapse tends to maintain current flow in the winding after the rotor
has passed through neutral and stopped generating. To get spark, we
open the points when the maximum magnetic flux change will happen, and
when the points open the current is arrested suddenly, the field
collapses violently, generating a large voltage in the secondary
winding. Big spark for the plug.
If the E-gap is off, the spark's strength is reduced and
roughness may occur.

Mag that are slightly mistimed can cause roughness, too. If the
engine's data plate calls for them to be set at the same TDC angle, you
want them real close to being together. If one is much later than the
other. the pressure rise in the cylinder caused by the first plug's
firing can get high enough to prevent the second plug's firing, and the
cylinder loses a bit of power. Sparkplugs need more voltage than mags
can provide to spark at high pressures.
Worn points cause resistance that prevents full current flow in
the primary winding. A worn capacitor can leak and reduce spark
intensity. An open capacitor can kill spark altogether, and one will
reduced capacity will burn the points. The Slick distributor's rotor
bushings wear and the rotor's finger gap can get too big and weaken
We've recently had trouble with AC plugs; the internal resistor
seems to be failing. Champs have had that problem for years.

Dan