I’m starting think there is something wrong with my motor wires…
It’s a outrunner from alien, and i also had to shorten them.
I just cut them to length,
Slightly twisted them so they stay together.
Added some flux (Rosin soldering flux , CAIG brand), it’s kind of a gel, and i really saturate the wires with it.
After that i just leave the soldering iron(40W) (with a bit of solder on it to maximize heat transfer) until the flux starts boiling, and start adding some solder (sn63-pb37 2.2%flux 0.0062" diameter)
It seems to melt the coating of the wires and tin them perfectly.