Well yeah. The lawnmower axle had a lot of reduction built in. Not enough...but a lot. And it was a large industrial weed-eater power head..they have pretty robust centrifugal clutches.
... the lawnmower has a belt between the motor and drive axle with a further reduction via pulley size ....
that would be like building a motor cycle with a direct drive sb 350 ...
Oh Wait some guy did that in the 60's with a 327 IIRC