In my '94 Brumby (https://imgur.com/BFFT3xz), which had been abandoned in a creek/ditch for a few years until last month or so, it mostly runs fine (engine bay with air filter removed: https://imgur.com/45ORu6H) , I began having issues with electrical stuff. One day, I came to it to start it, and after moving the wires around next to the battery a bit to make it work, I tried to turn the key, and it started, but stopped as soon as the ignition was released into run position, the engine stopped. I tried to start the engine again, but held the ignition half way, which allowed it to run, however after 20-30 seconds, a fire caught on the back of the carburetor, so I let go of the key and put it out with water. I am wondering what the part which the wire connected to it burnt out is called, and perhaps help with the ignition issues.
images: https://imgur.com/DmMepPs https://imgur.com/8e9CN2n
TL;DR: Brumby does not run without key held towards start, fire broke out and need help identifying what part.