Everblade- I'm sure it's a lovely engine but I very much doubt tinkerman's going to consider it an option- along with all the other lovely engines out there.
Tinkerman- For what you'd have to go through to use that big twin, you're much better off rebuilding your 13hp horizontal. Having to employ an RAGB or mower tranny will add weight, cost, and complexity. You will also have space constraints as these mower trannies are typically installed at a distance from the engine. Now, you'd be looking at shoehorning an already huge engine into the rear of the kart, and still try to make room for a tranny or RAGB and the associated driveline goodies required to make it work. Not only will it be a tight fit, but will add excess weight, robbing power and throwing the kart's weight bias further rearward which can adversely affect handling.
Most mower trannies are not stout enough to withstand the rigors of karting. Those that are can be pricey and still require some modification work.
Many walk-behind snowblowers' RAGB's are not only lightweight and relatively flimsy- they also tend to be worm-gear units. Worm drives can NOT be back-driven or they will detonate. By back driven, I mean applying power to the output, such as coasting. The rear wheels will try to "drive" the output shaft, and you'll be picking up bits of it for quite awhile.
I did lay hands on a 1.2:1 RAGB from a Bolens garden tractor snowblower attachment. It features an iron case and steel gears in a bevel arrangement. While perfectly suited for the task mechanically, it's a large, heavy hunk of equipment that's gotta weigh 10-15lbs, not including lube, pulley, sprocket, chain, mounting bracketry, etc. Good for a buggy, lousy for a kart.
Just some food for thought.
