The electric components
Fuse ( Hot wire)
Key switch (some go-karts use ignition switches)
Starter button
Solenoid switch (starter relay)
Electric starter

Electric starter system diagram


One function of the key switch is to act as a gate, when closed voltage passes to the starter switch.
When the key switch is in the on position voltage will be present at the starter switch.

The starter switch is also a gate switch , when depressed it allows voltage to pass to the starter relay.

The starter relay plays two rolls
1. Switch Side
When the starter relay receives voltage from the starter switch it turns on the solenoid (the solenoid is part of the relay switch).

2. Solenoid side
The solenoid creates another gate from the battery positive allowing voltage to pass through the fuse then to the electric starter.
Starter motor runs , circuit is completed as voltage returns to the battery through a common ground. (negative ground).