read my plug

[400excaleb]

i couldnt get my pic to show up good but
the thing in the middle of the plug and thing that runs over the top is light brown like a brown paper bag but the ring on the outter edge is very black, what do i need to change

[oldschool73]

If it runs good put a new plug in it and call it good. if the insulator in the center ( with the small metal tip ) is oily and wet you got issues oil fouled. or metal deposits stuck to it even bigger issues. brown is good. do a google search on plug reading and you should find all kinds of pictures that are good , bad , and just plain ugly! Also if the center electrode is really white you are most likely running lean or in a liquid cooled engine burning antifreeze which could be a head gasket, or cracked block. but on a 400 ex with no liquid cooling not an issue.If the plug is all sooty and carboned up it is running rich.

[oldschool73]

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.


found this on exriders.com look in tech info they have picture all credit goes to them hope it helps.

[hornetgod13]

You got it! The brown paper bag color is perfect. It's the porcelin just underneath the electrode is what you are sopposed to look at. The black residue on the outside threads is normal. Jetting can be a time consuming process. It's real satisfying when you realize you fianally got it.