Thanks again brutus.! If you look at the second green arrow to the lower right you will notice that the C-clip is missing from the throttle axle. This is intentional since the throttle axle will not move freely and will not close butterfly completely with this clip in place. The reason is that the return spring pulls the axle axially, forcing the C-clip to rub hard against the throttle body....! My intention is to have the butterfly pulled by the servo from fully closed to "full bore" and NOT utilise the idle speed adjustment screw on the carb. This enables me to shut down the engine with the throttle if need be. Does that make sense to you..?

"Save the glow engine - they make such marvellous gassers" ..!!! I like that brutus, myself having close to 100 glow engines amassed over many decades - just waiting to be converted to gas..