I’m not very familiar with the Z1 engine. I know it’s rare a CB750 crankshaft goes bad unless it’s really abused. Do the Z1 cranks fail often? With all rollers except for wrist pins I would think if it had oil it’s all good. The two strokes didn’t need much oil to keep the crank happy.
Perusing Facebook marketplace just really paid off KINDA. A 4 hour round trip and $130.00 YES $130.00, just scored me a Z1B 900 engine. Plan was to buy it regardless of condition hoping I’d get at least a good crankshaft out of it. I have to say if this possible I’m disappointed. Turns out the engine is a fresh (unknown years ago) build never fired. Can you be disappointed finding such a deal. Maybe I’m pleasantly disappointed. The goal was to get a crankshaft for this project. So now I wait till the generous member returns home and I can get my crank.
Engine is higher compression pistons. In the photos you can see sharpie numbers 2&3 on the pistons, the fresh cross hatch, ported heads, band new B8eS plugs, and Yoshimura “poppy” cams. I faintly see a B stamped on the cam ends. No clearance ground into either the lifter bucket nor cam cover areas.
It'd probably be a couple hundred in gaskets to put it back together if you take out the crank, but at the same time, it's good to finish a project instead of starting another. I pretty easily get four or five things on my hands if I don't stay on top of things.
Another option might be selling the engine - maybe someone would trade you for a good crank?
I'd be interested in seeing what that crank mic's out to. I suspect it's about the same. If it's better I'd use it, put it back together, sell it or start another project. My bike is still going strong 3 1/2 years later and will be installing my 1075 kit when I get it back from APE. I'll even use new emblems on the side covers.
Speaking of CC’s is there any way to find out the bore on this new to me engine. I don’t plan to pull it apart. I’m am going to pull the pan to visually inspect the lower half. Can you access the bottom of the block with the pan off?