Continuing saga of the ballast resistor - update No.2

[Courtney]

Ok had my cousin come by today, he is an engineer with the Royal Navy, and is responsible for little stuff, Like say, keeping nuclear subs running etc etc. :-)
Needless to say, he knows his stuff, and pulled out all my multimeters, schematics, yadda yadda, you name it.

Here's the scoop, when the resistor heats up it basically opens and kills the ignition circuit, so it's toast. I have never seen anyone diagnose stuff so quick, man he's good. The tough one is this though, and we're both stumped. We isolated the resistor from the circuit yet the bike still would not start, which is mystifying to us both. He said according to the schematics just jumping the resistor should allow a full 12 volts to the system but the bike still has no spark at the plugs. We suspected the TCI but after replacing it with a known good one it still won't start until that ballast resistor is in the circuit and cooled down to act normally again. All we can surmise is that the TCI must 'know' the resistor is in the circuit and won't start without it.

I'm glad to see that an electrical engineer of his calibre was just as stumped as me on that one. Unless the schematics aren't telling the whole story.

Stay tuned folks, new ballast resistor is on the way.

[CMA1]

I may not have this right, but here goes anyway....
Used to work on old Dodges.
The ballast resistor is by-passed for the 'start'... then comes on line for 'run'. There has to be something else not right, for 'starting'.. then the ballast resistor part of the circuit comes in after starter is disengaged. On the old Dodges that (what you are experiencing) meant replacing the relay.
I admit I haven't been into this bike much and I have a lot to learn, so maybe the wiring is all different????? I would check the wiring and fuses around the solenoid
My .02.... (Cdn money so I guess I still owe a couple of cents)
Good Luck

[Courtney]

No you are absolutely correct on that. We even disconnected the circuit to see if the engine would fire with the resistor out of the circuit, and the engine DID run with the starter button depressed, but as soon as you took your finger off the starter button, the engine croaked, just as it should, because the power then gets shunted to the resistor.
Don't doubt yourself, you are correct 100 percent. If you don't mind, check out the schematics on page 113 of the Haynes and see what you think. These use a diode I think to change the voltage to and from the resistor when the starter button is depressed.

[CMA1]

well Courtney,
I don't have the Haynes, I have the Clymer (and I know the diagrams are said to be not quite right) but here goes....
on the page for your SG:
One of the white wires from the generator is jumpered to the rectifier and to the tach on one side and to the relay. In the line going to the relay there is a switching diode(where it is doesn't show, but Anode towards the relay), the relay also connects to the fuel sending unit and indicator and ground for the tach light,regulator/rectifier and a "bunch of stuff" ... and goes to fuse 4 (R/Y wire)
On the ballast resistor: 1 red/white wire goes to the Igniter/starter solenoid/engine stop switch. The other R/W wire goes to the Igniter also and to the Ignition coils.
Got a good ground on the Igniter Unit?
When you jumper the ballast resistor connections use something heavy (I used to use a metal refill from a click pen with ends pinched tight) and don't run it a long time because it does get hot!
After checking continuity on the wires... I'd suspect that RElay, or maybe the Kill switch (?)
Then I'd doubt myself and go back to the manual...LOL
I know you probably checked all this already. I am just glad to be participating hehe Good Luck Bro'