Gilera 125 runner keeps cutting out, (crab heater?)?

A wee while ago my runner would not start , after i checked it i found there was a plug came out from the side of the carburettor i plug it back in and it was fine. But it keeps popping out so i taped it in which was fine but now it starts somtimes. am sure it is this cable but i dont know what its for. is it a carb heater? its on the side on the crab not the side of the exhaust , its black with a silver plug top. no liquids run through it. please help and thank you

stuart