I did this because I thought the Y/R needed to be grounded to activate the starter relay. Not the case as the Y/R wire coming out of the starter relay has power when I use a 12V test light.
The Y/R wire coming out of the starter relay/solenoid is one end of a coil, with the other end being the black wire, which has 12V when the ignition switch is on. When the starter button is pressed, the Y/R wire is indeed grounded, and the voltage drops to zero. The resistance of the coil limits the current so nothing gets burned up. The same thing with ignition coils and points; when the points are open, you will read 12V, or a test lamp will light, and when the points are closed, you will read zero volts, or the light will go out.
Thanks for sharing your fix!