If my bike wont start but does start when I use the wrench on the solenoid trick; does that mean I need to replace the solenoid? I'm having trouble working this out as I'm new to mechanics and trying to learn. If this is the case some people say its not the solenoid and its the starter relay. I cant seem to work out the difference because if you search for motorcycle solenoid parts and starter relays they look exactly the same. Any advice?
The "solenoid trick" pretty much guarantees that the solenoid is good. When you short it with the wrench you're simulating a start signal on the small terminal. When you do that the solenoid does its job, so the solenoid is probably good.
So now the question is why aren't you getting the start signal when you turn the key or hit the starter switch. Start by measuring the voltage at the terminal to see if you get anything when you ask the bike to start. Nothing at all means that you're got a problem upstream of the solenoid, perhaps a failed switch or relay (if they use one). A low voltage suggests a bad connection, could be a failing switch or relay or a poor ground. You can check for the poor ground by reading between the solenoid terminal and the battery ground post.