Yeah, that's a little spooky. Usually, I find some thrust surfaces in the crankcase that locate the crankshaft, and do not allow any sideways play. But it appears that some of the older motors didn't really need that much control since nothing is pushing or pulling on the crank shaft. The cam chain is in the middle and the primary drive is straight cut so no sideways force to speak of. Still, you gotta wonder whether there's some flexing of the con rods. Next time I'm at the race car shop, I'll ask some more experienced engine builders. Meanwhile, since it runs and sounds okay, enjoy! Cheers!