Triumph Repair: Spitfire ballast wire, ballast resistor, starter solenoid

Question
QUESTION: I have a '74 Spitfire and am 95% sure I have tracked the problem (starts but won't run) to a bad ballast wire. I'd like to replace it with an externan ballast resistor.
My diagram shows the wire between the switch and the + wire on the dost.
Without unwrapping the entire harness would you have an ideae where the ballast wire is located?
Thanks,
Smoke

ANSWER: Hi Smokey,
When they used a resister wire it was usually directly attached to the coil (+) and was a Pink w/white tracer wire. A second wire on the coil (+) was a white w/yellow wire which supplied power only in the cranking position and it came from the starter solenoid. The only wire on the distributor is the wire from the (-) side of the coil.
Howard

---------- FOLLOW-UP ----------

QUESTION: Here's my problem.
There are two wires on the + of the coil. One to the noise suppressor and the other is (I'm pretty sure) white w/yellow. It's pretty faded but the dominant color appears to be white.
The starter solenoid has several wires.
White w/red - start interlock
Three brown - +12v. power
Starter & battery cables
One more that I can't tell the color but assume to be the white w/yellow to the coil.
The switch is hard to get to but near as I can tell there is only one white w/pink on it (The radio feed ?)
There is a larger white wire on the switch that appears to go to the top fuse. There are 5 or 6 white wires on the fuse.
If I cannot locate the ballast wire would my electrical system be safe if I was to run an external resistor wired from the + on the coil to the top fuse?
Theoretically that would agree with the wiring diagram.
Thanks,
Smoke

Answer
Hi Smokey,
Yes, if the "Top" fuse is only on when the ignition switch is on.
The objective was to supply 12v to the 6v coil during start by the starter solenoid and then when the engine started and the key was released back to the run position, power would be supplied to the coil by the resistor wire which dropped the voltage down to between 6 to 9 volts to the 6v coil thus not over heat the coil.
When in use in the start mode the 12v supplied by the solenoid was not really 12v because the starter draw was enough to keep it down to 9 to 11 volts. Some Spitfires used a resister in place of the resister wire. As I remember they were about 1.5 ohm. Either will do, just so you don't have a full 12v powering that 6v coil.
Howard