I'm changing the motors on my Phantom 2 V+ V3. The motors came with the leads stripped a small amount and tinned. The stripped portion was small so I stripped some more insulation off and attempted to re-tin the wires. I have a lot of soldering experience, but I could not tin the leads. I use rosin core solder and even applied extra flux. I don't know if there is some kind of coating remaining on the wire or if its some alloy other than copper. I only did this with 1 motor. I believe I have a good solder joint to the part of the wire that was factory tinned, but more insulation is bare than I'd like. Any ideas on how I might tin these leads?