How To Read Spark Plug Colors


New Member
Apr 1, 2007
How to Read Spark Plug Colors (written by Atlantic Jet Sports)

In General: Reading spark plugs can be a valuable tuning aid. By examining the spark plug insulator color, an experienced personal watercraft engine tuner can determine valuable information about the engine's overall operating condition.

Normal: Grey to Light Golden-Brown Color

* This condition is ideal, the spark plug and engine air/fuel mixture are operating properly.

Dry: Black Soot Buildup

* Air/fuel mixture is too rich, the carburetor settings are incorrect, or the flame arrestor is dirty or has mounting problems.
* Spark plug heat range is too cold for the operating conditions.
* Ignition system problems causing a weak or intermittent spark.

Wet Fouling: Shiny, Wet, Black Appearance

* Excessive use of the choke (gas fouled)
* Prolonged low rpm operation (gas or oil fouled)
* Fuel to oil ratio is too rich (oil fouled)

Excess Deposits: Bumpy, Chalky Buildup

* Poor fuel quality
* Oil leakage into combustion chamber
* Improper oil used for premix/injected

Overheated: White, Blistered, Melted Electrode

* Lean air/fuel mixture
* Spark plug heat range is too hot for operating condition of the engine
* Plug is not properly gapped and/or torqued onto head
* Overly advanced timing

A detonation problem would show signs, such as silver specs, black specs, or melting or breakage at the firing tip.

NOTE: Signs of fouling or excessive heat must be traced quickly to prevent further deterioration of performance and to prevent possible engine damage.

this helps alittle for the people not familar with spark plugs, glad mine is normal condition.
Both are very good charts but i prefer the one lbwd posted they don't have a bunch of plugs saying good.
my plug is a soot black but it is all stock so idk y but when i put my uni air filter and uni air box vents should i rejet?
We won't be able to tell you if you need to rejet or not, your plug will tell you that.

But you might have to, more air means you need more fuel so it doesn't lean out an seize.

But like i said read the plug it will tell you weather you need to rejet or not.