traxxas titian and mm?

[ill_tempered_02]

I have a mm hooked up in my stampede and I had it hooked up to a fagio 540 6L. the motor works ok but I don't have spare cells or battery bars to make a 8 cell nimh pack, so I wanted to hook up a traxxas titian because they can handle 14.4 volts. I wired it up to be brushed W/reverse and hooked up the 12 cells. the car took off and wasn't to bad for about 15-20 seconds and then poof the motor started melting. I am wondering why it melted, and how I can run one of these successfully.