[haybaler]

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!

 

[haybaler]

Roller bearings, wow! in 1984, did Kawasaki have a few thousand bearings leftover from the 500 and 750 2 stroke engines?

I thought by then they would all have automotive type soft alloy split bearings.
Anyway, the bolt of the rotor should pull the crank against the thrust surface in the crankcase, but this engine has pinned roller bearings;
I wish I had one in front of me because it's tough to see how it works in any of the parts diagrams, or pictures of parts on Ebay.

Doesn't someone else have one of the older engines apart right now?

 

[haybaler]

Here's a pretty good picture of one from GPZ1100:

 

[haybaler]

The #5 bearing looks pretty well "trapped in there, so if the pin to the crankcase is secure, then there should be no side play, right?

 

[haybaler]

Good find, C-130; maybe relevant: removing and refitting crankshaft on GPZ1100