Hi Dave,
Yes some solonoids have 4 wires, the 2 heavy wires and 2 thin wires, one of the thin wires is a earth, the other is a positive coming from the start switch which activates the solonoid. If you can get to the solonoid an easy way to test it is, once you have found which thin wire is coming from the start switch, get a piece of wire long enough to come from the positive on the battery and touch it onto the thin wire you found coming from the start switch onto the solonoid. This should kick the solonoid in. Just for safety, remove the spark plug wire to prevent it from starting. If this test works then it indicates the solonoid is ok so then you go back to looking at the start switch
