Please check if the wheel is rubbing against the motor housing. There should be approximately a 1-2mm gap between the inside of the wheel and the motor housing. If there is not, please loosen the grub screw inside the throwing wheel (tightening it onto the axle) and then slide the wheel 1-2mm away from the housing, before re-tightening it.
If this is not the problem, then the bearing inside the motor may be causing this noise. It is not advisable to apply any oil or grease. In many cases, the noise will not affect the performance of the machine and can only be heard at low speeds. This can happen during normal wear. If it needs to be corrected, replacing the motor is the best option, so please call your local Spinfire distributor for further information.