Re: what did you do to your motorized bicycle today?
I had pretty much the saem issue with my old engine too because I really don't remember it having any side play when I had it apart before running it, but it did turn over nice and free when I checked it before putting it together for the first time, then after about 10 hours of run time on the engine I took the jug off to inspect it and that's when I noticed the play. Mine had about 1/8" play in it but I didn't see any other issues that could have caused it. I could only imagine what 3/16 to 1/4" of play could do to the case covers and cases tho... Hopefully the cases are ok and you can shim the crank with spacers.
Anyway, let me know what you find out when you get a chance to take it apart