In order of asking-

Chain rollers with side play- "normal" for these kits.
Casting error- Usually not a problem, but some sellers will replace the cylinder or kit if you let them know about it.

Now, "4 stroking" or 4 cycling sounds like a rough stacatto or firing every other cycle, as opposed to a smooth ""buzz" of the 2 cycle sound. If your engine four strokes all the time, it's too rich.

When these ancient tech piston ported two strokes are "right on" with their mixture, they will break in and out of the two cycle/four cycle sound at cruise or light load, and break into a clean two cycle "buzz" when you twist the throttle, or start up an incline.

Part of the reason is the crappy carb, and part of it is the "ancient tech piston porting". If you have one that runs in a clean two cycle at cruise, you are getting close to a very lean condition.

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If it ain't broke, and you mess with it long enough, it will be.