Lol. Just try those little eBay nitrous kits. They put a hugeass blast the first shot, but then slow down. And they're made for 49cc 2 strokes. So it should fit a nice large cc engine and still give it a nice burst of power.
A Honda 5HP doesn't come with a billet flywheel... they come with aluminum flywheels. I really hope it wasn't a GCV pressure washer, those flywheel's are like Briggs' aluminums.
I'd go for a Harbor Freight/Princess Auto 6.5HP, replace the rod and flywheel, 26lbs springs, Chromoly push rods, 22mm Mikuni and billet carburetor adaptor, and a air filter, and a little straight header.
Basically all you need to bring a Clone up to NO2 standards.