melting wires!?!?!?

[jokerjustin]

i usually run my revo in my track next to my hose every morning before i go to school. well today i wasnt running it hard and when it passed by me i saw a large puff of smoke!! instantly i ran unplugged my battery and tried to find where the smoke came from... i had directly soldered my motor to my mm and some of the "replacement wire" i used was bubbling and melting all over the place. the wire inside was completley black. its weird ive been using this exact setup for bout 2 weeks straight and ive run it waaaaaay harder than this morning... and thoughts on why this suddenly happened?