Well, you can't replace the seals on the crank w/o replacing the whole crank. somewhere, you probably have a slow oil leak. Better hope it's in your rotary shaft seal as that one is easily removeable compared to the crank. It's probably a slow leak and you may be okay to run it, but if you crank the engine over the way it is now with the plugs in, you'll hydrolock it. Suck all that oil out from the case. Rotate the engine to get the crank out of the way so you can get your sucktion tube right to the bottom of the case. May have to take the carb manifold (Rotary Valve cover) off. Once it's all out, turn it over with the starter, but have plugs out, and hold a rag above the plug holes. You'll spew lots of oil vapor. Be careful in taking off the Rotary Valve. Mark what tooth goes to what tooth so you can easily reassemble it later. If it is the RV seal, you'll see it weeping once you take that manifold off. If it's a slow leak, you will only see it after a few days or so.
