01 225 Optimax fouling plugs

[Ranger520vx]

A friend has this motor fouled the plugs last year so he replaced them. Then this year 3rd time out it started surging and had a knock just like last year. Plugs are covered in black soot and so is the prop from the exhaust. We checked the compression left bank starting at the top 90,90,82 right bank 90,90,85. So he put another set of plugs in it and we noticed that the filter for the air pump in the top of the cowling was pretty dirty so replaced it too. He took it out ran fine but plugs and prop were carboned up again. Any body got any advice. He runs Opti Oil in it and alcohol free fuel. Thanks

[Feathers and Fins]

Always leery of "ethanol free"

I Treat mine with Stabile no matter what or where I get gas. Also am certain to run the motor full speed at the end of the day plus the addition of an inline fuel filter between the tank and the engine.

[fishinwrench]

Check the air pressure at the Schrader valve on the port side rail (it should be 80psi)

Fuel pressure is checked on the other side (it should be 90 psi).

Lemme know what you get and we'll take it further.

[Ranger520vx]

OK the for the replys I will tell him and let you know the results.