Yet another question on the rebuild we are doing!

Should there be any play in the sprocket that is attached to the crankshaft? Logic seems to say no, since any about of delay could throw off timing (wouldn't it?), but we're having a hard time finding the exact answer to this in the manual. You can turn this turn this sprocket by hand maybe 3 degrees. Would this also account for the large timing chain stretch?

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Natalie