Hi Dave!
At first you must show that the "GROUND" from the Batterie is correct connected with the engine!!!!!
All problems with the electric starting with a bad ground.
Normaly is ab very small ground-cable on one bolt on the engine.
At all my machines i have put a big one directly zu the bolts on the starter.
i think, when you have the ground contact good placed, the solenoid will works fine......
Much fun, and when you be worry, get an car electrical, he can help you
Greeting from germany
(Turbo)Klaus