Rob,

It's not a resistor, it's a diode. If it was a resistor, it wouldn't matter which way it went. But it DEFINITELY matters which way a diode goes. I don't know about all Walkera 4-in-1s, but the one for the 22E has an internal diode so the one on the motor isn't really necessary. It's probably better to not have one at all than to have it installed backwards. The end with stripe on the diode should be connected to the positive terminal of the motor (which may be marked with a '-' if you had to reverse the wires to get the motor to spin the right direction). You should use a voltmeter to verify polarity of the motor terminals before soldering on the diode.

-JT