Most vertical shaft lawn mower engines will not run properly without a blade on them. The reason is because the flywheel is not heavy enough by it’s self.
So the only thing it’s really good for is to put on another mower. Try to sell it.
Ah, the B&S engine is balanced for the rotational load of the 21 blade at a constant (relatively) demand. But can I get some use from it is my question, sir.