There is a big difference there.
Yes he had a 9hp factory engine. It's larger and setup to make the power at to low of a RPM. So it's more weight, and less RPM.
You have lighter weight, and higher RPM. That will win every time.
Now if he had a 6.5hp Honda, or 7hp Subaru with the same carb you would be in trouble. Same weight and same RPM, or better. The good thing that helps the briggs is the larger cam, and the Animal has a aluminum flywheel.