Without being there it's hard to root cause.
I always check flatness of mating surfaces and reverse dome any sheet metal cover holes. When you nip up the bolts you get a nice compression
of the thin paper gasket
I also like to use a good gasket adhesive
mainly to keep the gasket in place during assembly and to stop it tearing on removal
As for crank seals
checking for grooves on the rotating bits and ensuring the seal is square are key. I have a motorsport background. Most of the hi output hi revving engines are very fussy in this regard.
I have a 4-236 that doesn't leak and has clean oil
with nearly 4000 hours. Very tough engine
. Simple, mechanical and no electronics
I am obsessively ocd about leaks
and cleanliness. Oil
and filter changes every 50 hours, never run cold or too hot under load and engine
tension check whenever I feel like scratching that itch.
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