Jetski fouling spark plugs within minutes

Sevs753

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My neighbor has a jetski from the '90's this is fouling spark plugs within minutes. He said that he can't even get to open water before the plugs are fouled. The engine is a 2stroke 2 cylinder engine. The gas and oil have their own separate tanks. One thing he did say is that a while ago, he was adding oil and after adding about a pint (his estimate) he noticed it was yellow when the oil he's added before was purple-ish. He said it was a different brand of oil than he usually uses but is supposed to be compatible with the engine. After he noticed the color, he didn't add anymore.

To me, it sounds like either the jetski is mixing in too much oil/not enough gas or that yellow oil is creating problems.

Any ideas? I suggested that he drain the oil in the tank and refill with the stuff he normally uses but I want to cover all possible causes.
 

GRtak

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Has he recently changed plugs and put in the wrong temp plugs?
 

GRtak

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Two strokes are really sensitive to the temp range of the plugs. They have to be far hotter than a four stroke to burn off the oil, yet cool enough to prevent pre-ignition.
 

devil500

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Has he changed the jetting on the carburetor at all? Could be that the fuel mixture is too rich so he might need to lean the motor out by adjusting the jetting. It could also be that the new plugs are the wrong temperature.
 
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