Can you speculate why someone would have added a second solenoid?I missed this post.
Someone could not have bypassed the solenoid, as that is required to engage the bendix (gear Drive) for it to start.
What they have done is added a second solenoid that is more than likely feeding power to the first solenoid.
You can very easily check the starter and the starters solenoid and jump it like you are doing to the top solenoid.
Just jump from the battery cable on the starter to the small solenoid terminal.