Adding a relay for "remote" start 

So you're building a kart from scratch or throwing a new (to you) motor with electric start in an existing kart without any switches up front to start the engine and wondering how you can start it from the driver's seat. Check out the solution I came up with the same issue in a different application.
Running heavy enough wires to the front to bridge the starter relay terminals "safely" just isn't cost effective or smart. You'd need a heavy gauge wire to and fro and you'd have 12v+ up there which just isn't all that safe.
Here's where automotive relays save the day!
In this configuration, terminals 85 and 86 receive the "input" signal (power and ground for activation). 12v+ comes from the main battery post to post 85 (white wire) and negative will come from my negative momentary switch up front in to post 86 (black wire).
Post 30 (blue wire) also connects to the main battery post for bridging the terminals. Post 87 (yellow wire) goes to the other terminal on the main starter relay.
When the black wire on post 86 is grounded, the relay bridges the terminals and starts the engine!