[Machman]

The starter will ground through the engine, so be sure your ground wire from battery is connected to the engine.

If you run your battery negative cable directly to the engine (which I do!), don't forget to put an equally beefy cable from the engine to the frame / body (I usually do one to both, just to be sure).

Paying attention to the "ground" side of your wiring will pay off in the end...