Looks like you have the engine battery, and possibly the switch, back with the receiver battery and receiver, and possibly the throttle servo up front. IMO, this is backwards. All electrical components for the ignition (including the battery, ignition box, and switch) should be up front and as far from the control components (receiver, servos, switch, regulator, etc) as you can get them. I also always mount my throttle servo (it is part of the control system) back with the radio and use Nyrod to go to the engine. Interference can be sent through anything connected to the ignition box. Also make sure no metal is vibrating. I see you used nylon connections to the carburetor and that it good.