As per the last two responses, fan should be helping the natural airflow, so pushing air towards the back of the bike. Swapping the wires will change direction. Just thinking... If you were overheating and the fan wasn't turning on, have you checked circulation? Faulty thermostat? The thermo switch for the fan is usually housed in or around the radiator, and the radiator wont get hot if there's poor circulation.
Only two wires to connect it up and you may have got it wrong. Reverse the two wires ad see if it reverses the direction of spin.
You view the fan from behind looking in the direction of travel. The fan should turn towards its forward most point of the blade.