Understanding Spark Plugs
Understanding Spark Plugs
For those of you that don't know how your spark plugs should look take a look at this site.
www.harleyhelp.com/sparkplg.html
www.harleyhelp.com/sparkplg.html
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
yes and no. he cites a mixture of facts, rumors and conjecture.
for the novice, and in fact most riders, "reading plugs" is impossible unless there are real mechanical problems with the motor.
modern efi systems and fuel additive packages ( incl ethanol ) make all plugs look "lean" by the standards of the 70's with points ignition systems, centrifugal weight advance, carbs and lead for octane ( the pictures must be from an old manual- they show lead deposits on the plugs)
to get any data from a plug, a new plug has to be installed and the motor run at the rpm and load of interest, then pulled and observed.
...then a new plug for the next rpm range of interest etc.
the part I do agree with is that there are no magic plugs- if a plug alone could increase power or mpg GM, Honda and Ford would love to advertise higher power rating and MPG to meet cafe standards- so they'd use them if they existed.
on a crap old motor an iridium or platinum tipped plug can burn trough soot and deposits.
....and some plugs may not properly work with the ECM activating the anti-knock spark retard and reduced power
mike
for the novice, and in fact most riders, "reading plugs" is impossible unless there are real mechanical problems with the motor.
modern efi systems and fuel additive packages ( incl ethanol ) make all plugs look "lean" by the standards of the 70's with points ignition systems, centrifugal weight advance, carbs and lead for octane ( the pictures must be from an old manual- they show lead deposits on the plugs)
to get any data from a plug, a new plug has to be installed and the motor run at the rpm and load of interest, then pulled and observed.
...then a new plug for the next rpm range of interest etc.
the part I do agree with is that there are no magic plugs- if a plug alone could increase power or mpg GM, Honda and Ford would love to advertise higher power rating and MPG to meet cafe standards- so they'd use them if they existed.
on a crap old motor an iridium or platinum tipped plug can burn trough soot and deposits.
....and some plugs may not properly work with the ECM activating the anti-knock spark retard and reduced power
mike
Last edited by mkguitar; Mar 7, 2012 at 01:19 PM.
Ultimate HDF Member
Joined: Jun 2009
Posts: 6,932
Likes: 4
From: 46th State, USA
I think this information is a basic rule of thumb to go by. The conditions of the plugs will give you a good indication that something is not exactly as should be, considering all factors.
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