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1. 08:09 AM - Spark Plug Repair! (923te)
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| Subject: | Spark Plug Repair! |
I googled "Slick Magneto Spark Plug Resistance" and got some interesting lin
ks. I never thought about replacing the resistor in my Champion plugs! Might
try that today. Take the massives out of the engine and use their "good" re
sistors in my fine wires...
http://www.aircraftmagnetoservice.net/id18.html
A new resistor type plug should read between 800 and 1200 Ohms
Remove and replace any plug that reads 5000 Ohms or more.
http://www.sacskyranch.com/eng11.htm
2. Incorrect spark plug gap(s). Fouled spark plugs. Broken spark plug cerami
c. Too much spark plug resistance, normal 1,000 ohm, too much is probably 10
,000 and greater.
This very interesting, from a Lancair list guy who talked to a magneto tech:
http://lancair.net/lists/lml/Message/56111.html?Language
> Then we started talking about spark plugs: I mentioned my plane has Champ
ion fine wire plugs. He said all plugs have an internal resistor, and for s
ome reason the resistance of many Champion plugs seems to increase as the pl
ug ages. Once the plug has been cleaned, the resistance can be measured wit
h a standard ohm meter between the center electrode and the connection insid
e the plug barrel -- all new plugs should have a resistance somewhere around
800 - 1200ohms. If the resistance ever measures above 5000 ohms, the plug s
hould not be used. The fellow told me plugs having too high of a resistance
can/will cause misfiring and potential problems with the magneto coil and o
r plug harness. A spark plug bomb tester might show this plug as good, so t
he ohm meter test should always be performed every time the plugs are servic
ed.
>
> Unlike an Autolite plug, a Champion spark plug resistor can be changed. L
ook inside the barrel of a Champion plug and notice the slotted screw. Remo
ve the screw and the resistor will fall out: it looks like a slug of carbon
about 1/2 inch long and maybe 1/8 inch diameter. You can put the ohm meter
on either end of this slug and measure the resistance -- this is the elemen
t that needs to measure from about 800 to 5000 ohms. The resistor is appare
ntly common among all Champion plugs so he recommended visiting your pile of
old plugs; removing the resistors; and saving the resistors that measure "g
ood". When you run across an otherwise servicable plug whose resistance is t
oo high you can change its resistor for one from the "good" pile. He says t
his can cure a host of otherwise mysterious "rough running" problems and for
estall future problems.
>
> He said some Reno racers remove the resistor and replace it with a piece o
f copper wire to get a much hotter spark for racing. Says it wears out the s
park plugs very quickly -- but does make a performance difference. Is this t
rue?
http://mechanicsupport.blogspot.com/2009/09/rough-engine-on-left-mag-nothing
-you-do.html?m=1
Spark plug terminal well showing arching lines. Plug lead is arching to grou
nd by way of the plug metal shell. Replace plug. At the bottom of the well t
here is a contact. Check spark plug resistance by placing 1 end of the ohm m
eter lead to this contact and the other end of the lead to the center electr
ode on the firing end of the spark plug. Resistance should be 800 to 1200 OH
MS. Replace any plug above 5000 OHMS.
This is what the resistor looks like inside a Champion REM40E spark plug.
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