Post some more pictures of the carb flange and other side of motor base, please. Also, post a few of the crankshaft. Are there any markings on the crank?
I have never had an L motor apart, so below is speculation.
To me, this looks like a home modification, but Simplex was in transition from the rotary valve to the model M crank, where the intake mixture passes through the center of the crankshaft, so anything is possible.
Is the inside bearing a sealed bearing, or does it have a removable cup? According to the manual, both bearings should be tapered.