Wire Sizes?

Okay, my wiring issues are becoming more and more apparent. I replaced by broken rectifier and shortly there after one of the bullet connections on a positive lead terminal literally melted. I am thinking something is wrong with the wiring and I would love to just redo the entire thing.

Does anyone know the breakdown of the wiring sizes for a 1976 KZ400? I have seen a couple posts with sizes but I am not sure if they are right for my bike (I wish the manual would tell me).

Also, should the negative and positive wires from the battery both be 6 AWG? The black is 6 AWG but the red is like 12 or smaller, should they both be the same? Maybe this is why the white bullet connection melted.

Thanks!

Your bullet connection melted because that's the point where the resistance was. If the wire was to small then it would be melting, not the connection.
Bad connection at the bullet connector done you in.

Any poor connection will create heat, melting insulation or,sometimes connectors & fuse clip holders.