Mass probably isn't your issue. If you manually turn it a couple revolutions will it take off? If so you may need a starter type circuit or that bigger ps to get it to work. Also keep in mind that stronger magnets can mess with the motors magnetic field which can prevent it from running. Metal washers can help to shield it from interference. The best one I've made had issues like that from super strong magnets and it took several to provide enough shielding for the fan to run correctly.