what are the obvious coloration on plugs to tell if they are
lean ,rich, or good enough

 

white=lean
black=rich
brown/goldish=normal

 

Tan Colored: a tan colored spark plug means that the engine is running normal and the air/fuel mixture is correct.

Black Dry Fluffy Colored: the black fluffy deposits are from a carburetor that is running too rich (too much gas) or excessive idling. Black smoke coming from the exhaust is a sign of a rich air/fuel mixture. The rich air/fuel mixture must be repaired before installing a new spark plug. Common causes for a rich air/fuel mixture are:

* dirty air filter.

* air mixture screw needs adjusting.

* choke is sticking.

* carburetor float height is out of adjustment or float is sticking open.

Black Wet Sooty Colored: the wet sooty deposits are from oil that is leaking past the piston rings or valve guides and burning in the cylinder. This engine will have blue smoke coming out the exhaust. It is a sign that the engine will need rebuilding. If a new spark plug is installed it will foul and quit working. Common causes for this problem are:

* Worn piston and rings.

* Worn cylinder bore.

* worn valve guides.

White Colored: a white colored spark plug is result of engine overheating. Failure to repair this engine will result in severe engine damage. Common causes for this are:

* Incorrect spark plug (too hot heat range).

* Low octane fuel.

* Timing is not set properly.

* Cooling problems, (dirty cylinder fins, no or low water if water cooled, low or no engine oil).

* Carburetor air/fuel mixture is too lean (too much air).





[Modified by ZC_CRX, 8:30 PM 12/7/2002]