Weird relay issue??
 

1985 honda fl350R
Trying to get it started.
Broke the pull rope so need to fix the starter circuit.
Traced 12V from batt all the way back to starter relay.
All good until I connect the wire to the relay.
Then 0V.
Don't understand how that can happen.
Unplug wire at relay and get 12V at wire terminal.
Plug back in and get 0V at same exact point.
Bad ground?
Bad relay?
Had to do the walk of shame when she wouldn't start!

bad ground. you have an "apparent" voltage of 12, then while under load it fizzes out.

High resistance in the 12volt supply ie bad connection

(keep it out of gear obviously..)

You can jump past the key/relay/solenoid with a jumper cable direct to the starter solenoid positive terminal.
That should engage the bendix and spin the engine.
If there is proper spark and fuel it should start.

Are the readings Key-on, or in Start position for the ignition switch?
Control side, or Load side of the relay?

0 volts would indicate electricity is passing through the relay to ground somewhere when the wire is connected. The load is elsewhere. The flow undetermined.

As mentioned it could be not enough amps to activate the relay or solenoid due to a poor ground or positive side connections.
You can jumper another new ground from engine/chassis/battery neg easily.
A dozen new grounds won't hurt anything.