Can it be connected to the throttle butterfly on a carburetted petrol engine?
Yes. The GS740 and GS740-3P are also used on petrol engines; the cable-pull servo connects to the throttle butterfly lever of the carburettor, and on a diesel engine to the fuel pump lever. The requirement is that the lever is mechanical and can move freely. The choke, the idle screw and the carburettor's own settings are not changed, the kit only drives the position of the butterfly.
The connection point changes with the engine type but the logic is the same: the cable is connected in parallel with the point the throttle lever pulls.
- On a carburetted petrol engine the cable is connected to the throttle lever on the butterfly shaft.
- On a diesel the same connection is made to the fuel pump lever.
Points to watch in practice:
- Idle is not set by the kit. The lower limit is set by the engine's own idle screw; the kit pulls the cable upwards from the idle position.
- It is not connected to the choke. The choke is for cold enrichment, it is not part of the speed adjustment.
- The return spring of the butterfly must be sound; if the spring is weak, the butterfly will not return fully to idle when the cable is released.
- The cable must be tightened so that it is taut at idle, with no slack left.
One point should be stated separately: on a carburetted engine too, the kit does not act as a governor. Small petrol engines mostly have a mechanical governor and that is what determines the speed behaviour under load; the kit only carries the butterfly position. Stopping the engine is likewise not the kit's job and must be built through the ignition/fuel shut-off.
Full topic: Electronic speed and throttle control on diesel engines