Regarding the carb, there is no real factory setting, it can differ a lot regarding exhaust, and fuel. If you can start is just adjust it where needed.
Most of the time with engines is setting all needles to flush to make it startable.
Regarding the switch, do not use one!
Just use a male-female connector like a Futaba servoplug and just let it hang somewhere without sticking it to the chassis or servo. Also use a spring or a small hairband on the carburator, when loosing power it will pull the carb to a close position.
Speed is only fiction but a 130+km/h MRS4 is for real.