Topic: Reading Spark Plugs

[Chrisboden]

Ok, now I hear a lot about rich and lean, and I understand that (rich is a high fuel to air ratio, lean is a low one), and, correct me if I'm wrong, but people figure out their mixture by stopping the engine and looking at the electrode of the spark plug.

But for the life of me I can't figure out how in the hell you can tell by looking at the plug.

What are you looking for?

What else can you read on a spark plug?

How, in detail, is this done?

[cb750_chris]

Black soot = rich.
Bone white = lean.
you should get a little bit of a brownish tinge on the white part if all is well.  Don't check them every five min.  Do a little riding between adjustments to get results that you can go on. 

Other problems can show up on the plugs as well like oil fouling.  Most manuals have a few pictures of damged and oil fouled plugs. 

[Bob Wessner]

Here's a plug reading reference chart as well;

http://www.unitedbearing.com/CHAMPIONSPstory.html

[MetalHead550]

This is interesting too.  You like technical stuff right?
http://www.strappe.com/plugs.html

[bryanj]

You take the plug temperature from the colour of the centre porcelin and the mixture from the colour of the flat steel end where the earth electrode comes from. Ideally  tan brown and light grey respectively

[Chrisboden]

This is interesting too.  You like technical stuff right?
http://www.strappe.com/plugs.html

Excellent read! Thank you

Dr.Duck