400 gas smoking

Paul in WI · Jul 1, 2008

My 400 gas motor smokes when I rev it up with or without a load.
Comprestion is 140, 145,145,145. Doesn"t use oil.
It keeps fouling the #3 plug and the plugs are real black in color. Have to keep cleaning the plugs so it will not miss after about 10 hours of use.
Could I have bad valve guides?
Any ideas

rustyfarmall · Jul 1, 2008

The valve guides would be my guess.

bob farrell · Jul 2, 2008

I would think if it were valve guides the smoke would be bluish in color and there would be at least some engine oil consumption. If the smoke is black, even without a load, I would think it is running way too rich on fuel. You may have incomplete combustion (due to too rich air/fuel ratio) therefore the black smoke and the carbon deposits on the plugs thats fouling them out. Adjust the main fuel screw on the carb and see if that helps. Also any restriction in the air intake will cause a too rich condition. Service the air filtration system - including the piping. Late timing can also cause incomplete combustion. Good luck and let us know what you find. bob f.

Paul in WI · Jul 2, 2008

Well the carb was set way too rich. My carb rebuild book said to set the screw to 3 full turns. Well my motor likes it at 1 to 1 1/2. At 1 1/4 it stopped smoking and still had plenty of power.

Will try this for a few days and see what happens

Thanks for all of your help on this.

400 gas smoking

Paul in WI

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rustyfarmall

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bob farrell

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Paul in WI

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