It sounds like you have the original FT 120 which had a metering carb and can be identified by the letters FT 120 embossed on the right hand side of the crankcase. The low and midrange on this carb left much to be desired in that the idle mixture had to be set very rich to allow the engine to accelerate properly. You will probably have to use onboard glow to get a decent low and midrange.The later model had the letters FT 120 II embossed on the right hand side of the case. This engine had the airbleed carb.