deason, yes the seals on the main bearings. They use integral rubber seals on each side of both bearings to seal the crankcase and this is common to most engines today. The rear seal on the back bearing was missing so I assume it had been removed before assembly. This was also common with some engines assemblers. These days, most leave all (4) seals in place. No separate seal in this case.On a related topic, if the bypass action is weak you may also want to inspect the backplate gasket and make sure the cylinder base gasket is good and the base bolts tight. Weak or no bypass = no run.

Speedracer, deason and I have had several PM conversations regarding this engine so I have had more info than what appears in this thread.

deason, Speedracer knows his stuff so trust his opinions and suggestions.