Lots of things you can do and all will boost the output, ONCE
Then after it goes Bang the output will be very low.
These engines are build down to the lowest possible price.
Thirty years ago the crank & rod would take the extra load.
However computer modeling now days means that the parts are the smallest, lightest & weakest that will barely handle the load till the warranty expires.
And then there is balance or rather lack of it.
Beef up the output and your mower will spend more time going sideways than forward.
Search "racing mower engines"
Lots of good information but if you tote all the replacement parts you will find the only original bits are the crankcase castings and even they get modified.
If you need more balls, get a bigger engine.