Some of those tiny engines do actually make enough power to do some work.
The Conley Stinger 609
for example allegedly makes ~5.5HP @ 9500RPM or 9HP with optional supercharger.
Converting Horsepower to Torque is: (HP * RPM) / 5252 = TQ
That works out to 9.5 ft/lb @ 9500 or 16.3 ft/lbs with supercharger. That's probably not that engine's peak torque, either.
That's considerably more power than many engines used on our bicycles, in 14*6*8¼" (14x6x10" supercharged).
Of course it's crazy expensive and who knows how long it would last before needing an overhaul. One of us needs to win the lottery to find out