Speedy, to give the motor reciprocating mass to test with is fine. Over time would be the worry, although, as long as you know it's spinning true and the bolts are secure, I can't see why it won't work. I would check after each mow for the first few goes though.
Hope you find an original disc soon.
Tyler, have you got the best one out of six on Kermit the Wayfarer?
