These are petrol bikes right... So you're confusing a carb heater with a glow plug? (Diesels)
Carb heaters are installed to prevent carb icing, and aid the combustion of the fuel in the winter (below 10 degs C). They do come on with the ignition switch if the temp is below set value but don't sit there with the ignition on waiting for the fuel to heat up. Fire up the bike straight away and get the fuel thru the carbs as it warms.
