What you want is a system that uses a wire within a coiled cable to move the throttle plate in the carb. These are sold as "choke cables" at auto parts stores. You normally make a "Z" bend in the carb plate end but mounting so the pedal works the cable BOTH ways is up to you. Somewhere in the system, you will need a spring or 2 so when you take your foot off the pedal, the engine slows down. This is a more critical part than the ability to push down on the pedal/cable and make the engine speed up. It's not just that you might lose control and hit something, it's also that the engine can overspeed and do nasty things like break connecting rods. So make sure it will slow down as well as speed up.