How in HECK to you figure HP on a B&S engine?

https://search.aol.com/click/_ylt=A...karting//RK=0/RS=cx602cK64qY5seVDvvYuOu8p21w-

Bob's 4 cycle Kart Forum.
Just about any 4 stroke formerly industrial type single or twin engine used for fun motor sports is in there.