Autoelectrics: Testing components off 12v battery
When everything is working correctly, the fuse doesn't do anything. The fuse is there in case something goes wrong and a component that should "only use as much power as it needs" starts to use way too much. If this happens then the fine wire in the fuse gets hot, melts, and saves the rest of your wiring from burning out.

The components in your motorcycle are designed to work with a 12V circuit, so it's safe to connect the battery directly to the starter solenoid coil (as long as it isn't faulty).

It's not safe to connect the battery directly across the starter solenoid contacts. These contacts are a switch to supply power to the starter motor. The starter motor will draw as much power as it needs when the starter solenoid contacts are closed

If you needed to use an LED in your motorcycle, you would add a resistor to the LED and package this as a single part, so that the part (LED + resistor) would only draw as much power as it needed.

Some parts do draw more power than they need. Often there is a "ballast" resistor in series with the ignition coil primary. This does the same job as the resistor in your LED circuit. It limits the current in the coil when the motor is running. During starting, when the battery voltage is drooping because it's powering the starter motor, the ballast resistor is bypassed to increase the current in the ignition coil