I have one of those Tecumseh 4 stroke mowers, and it too leaked from the valve cover.
I am not a huge fan of all those stop leak in a bottle products.
You can just take the cover off and make a new gasket. Either buy dedicated gasket material, or weet bix box cardboard works fine in areas such as this where heat and pressure are not too great.
Of course, donβt think that the cheaper method works for things like head gaskets.....
Last edited by twostroker; 07/01/22 03:32 PM. Reason: Spelling fix