Typical KZ starter clutch.
Pics 3 & 6, turn the rollers 90°, you can see the wear marks.
There should be a spring behind that little rod.
Push the rod back into the hole with a small screw driver.
Insert rollers in hole they should be sitting the same way as those Allen head bolts.
Take the drive gear and incert it into the starter clutch, turning as you go.
If rollers pop out,reinstall them and maybe add a little grease to hold them in place.
Once drive gear is in place it should turn one way and not the other to be functioning properly.
When you pick up the assembly to install it on on the engine don't let it come apart even a little or you could be starting all over.
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