Bought a used ofna stainless starter box for my new 1/8 scale in great condition. It came with 2 used old 2800 6 cell stick packs nicd. They charge but being nervous of their age I bought 2 5000mah 2s lipos 30c. Charged them up and now the wheel turns so fast but the motor sparks upon running the box at the start and when it ends. Is that normal? I only see it when I turn the box upside down.