[Rhoderman]

Check your 12V supply. Is the battery low, or have a dead cell?

If the battery seems okay, try running a wire directly from the coil + side to the battery + side and see if that helps. That would quickly rule out the connection from the battery, to the switch, to the coil. No need to remove the old wire since you're essentially paralleling it.

The coil also has to have a good ground, as does the battery. Check the battery minus, and where it attaches to the frame. Make sure the engine is well bolted to the frame. Disconnect the cable and scrape the metal and put it back together.

Hope this helps.