has it blown?
if you turn the blades with your fingers through the hole do the fins scrape the casing? if so the casing is touching the fins and causing the noise and it will blow
if thats the case take the motor out and try to pry the casing away from the fins until they spin freely
if its not that maybe someone else can help
best to always spin the blades through the hole with your fingers before you fit it so you can see if they spin freely, that way you can check its ok on arrival. They are suppose to be tested before sending out the factory