How to Do a Valve Job on an Onan P218

Find the rectangular iron valve cover on the left side of the Onan P218 engine. It will be situated near the carburetor. Remove the bolts on the cover with a socket wrench, then set the cover aside.

Use a Torx screwdriver to loosen the screw in the middle of the bolt on the top rocker arm. The rocker arm, bolt and screw become visible once the valve cover is removed.

Use a feeler gauge to discern the necessary adjustment to the top rocker arm. Attempt to slide the gauge under the left side of the rocker arm. Loosen the bolt on the rocker arm with your socket wrench, if the gauge will not fit under the arm. Continue to loosen the bolt until the gauge slips under the arm, but do not loosen it so much that the gauge is not pinned beneath the arm once it slides in. Tighten the bolt slightly, if the gauge moves too freely under the rocker arm.

Retighten the Torx screw with your Torx screwdriver once you have the top rocker arm adjusted appropriately.

Perform the same procedure on the Onan's lower rocker arm as you did on the top rocker arm.

Set the valve cover back into place and secure it to the Onan engine with its bolts and your socket wrench.