I've replaced 2 or 3 case cover gaskets to correct this problem(on Club Cars & Ezgos) both),over time they will "suck" the gasket in on the top of the crankcase & cause a massive leak.We had an outstanding engine rebuild guy here that would take a center punch & "dimple" both sides of the gasket face in these areas so the gaskt would have something to hold on to,he passed away a few years ago but he really knew the ins & outs of all these small engines
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