Spark Plugs

hoser · Posted: 29 Sep 2004 03:59 pm Post subject: Spark Plugs

Here are some old plugs I cut the metal off of to expose the porcelain

The plug on the left is way too fat you see black on the tip your jetting is
way off you need to lean out your air/fuel mixture the second plug is
also too fat but you notice the black only goes up about 1/2 way then
it is dark brown the 3rd plug is what I call normal but the smoke ring at
the bottom is still about 2 x wider than it should be the tip is almost tan,
if this was my plug I would lean it out some more, the far right plug was
not run long enough to really read but you can see the smoke ring at the
bottom starting to form (tip or red arrow) depending on the old plug I
would not panic and continue to run this plug with the current jetting to
see if it turned black or tan closer to the tip , when your jetting is right
that smoke ring at the bottom will be about 2x wider than you see in the
picture, the rest will be real light tan, this is safe, during race conditions
all white with the smoke ring at the bottom is ok, I have run this way
many times.

hoser · Posted: 29 Sep 2004 04:07 pm Post subject:

Here is another view of the plug on the left, you can see that area the blue area
is pointing to has no color, looks new it is running so cold from a rich mixture
it wont change color, green arrow is pointing to the black unburned oil that sticks
to what is hot, the porcelain is hotter than the bottom of the threads.

hoser · Posted: 29 Sep 2004 04:13 pm Post subject:

More info on reading the plugs

PilotHawK · Joined: 28 Dec 2003 Posts: 245 Location: Knoxville, TN

Here is an article on the same topic.

http://www.strappe.com/plugs.html

PilotNut · Joined: 19 Dec 2003 Posts: 420 Location: Howell, New Jersey

Great info Hoser - Thanks! It's also good idea to remind folks, as you did me last weekend, that before you dive in and begin jetting the crap out of your machine to check other possible causes of a fat or lean situation (i.e. dirty/clogged air filter, proper gas/fuel mix, etc.). It seems many (myself included) are way to quick to blame improper jetting for their performance problems when it is sometimes a much easier fix.

PilotHawK · Joined: 28 Dec 2003 Posts: 245 Location: Knoxville, TN

one thing on pilots i have seen before that may make them feel like they are very rich is a bad spark plug boot. that one took a while to figure out, but a new boot cleared everything up!

hoser · Posted: 01 Oct 2004 12:33 pm Post subject:

Here is a new plug run for about 1 mile at high speeds, see the smoke ring but
nothing on the tip, pink arrow shows where the coating on the reach is burning
back . Jetting is a little on the rich side.

hoser · Posted: 01 Apr 2006 05:53 pm Post subject:

Another pic.

Toyman · Joined: 01 Mar 2004 Posts: 172 Location: Wichita, Ks.

This is invaluable information. I know for certain I have all of my cars jetted rich as I've toasted many engines from jetting to close to the limit.

My plug chops show very dark brown insulators.

My question is how much harm is there from this practice?

hoser · Posted: 02 Apr 2006 07:59 am Post subject: Re: Plug reading

Toyman · Joined: 01 Mar 2004 Posts: 172 Location: Wichita, Ks.

Hoser; From running carb. jetting rich. Any harm in this other than a lower performance level from the engine?

hoser · Posted: 02 Apr 2006 07:55 pm Post subject: Re: Plugs

Toyman · Joined: 01 Mar 2004 Posts: 172 Location: Wichita, Ks.

Oh yeh, I've had that sensation several times.

I have a distroyed piston collection.

They always run their best right before they melt down.

This is why I jet alittle rich but worried maybe there may be some harm from carbon buildup etc.

I run it pretty hard at times so I'd be surprised if there was much.

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