Do you have the 4 wire plug that plugs into the solenoid? In the pic, the bottom 2 positions appear to be connected, so that would be where the solid red wire that supplies the ignition switch, and the red/white wire would be from the output of the rectifier, providing the charging current to the battery through the fuse. The upper 2 positions would be the solenoid coil terminals; 12v on one and ground on the other when the starter button is pressed.