wire question

[oldyam80sg]

Unless I'm reading it wrong doesn't the wires from the ballast resistor(red/white) eventually go to the TCI unit.So if i trace the TCI unit wires shouldn't i see a Red /white wire?

[boyat68]

oldyam80sg:

The schematic shows that the two r/w wires make it back to the igniter unit,(TCI) transistor control interface. Looking at the Ignition System circuit diagram in the Yamaha book, it shows one end of the resistor hooked to both sides of the I. G. Coil, and the other end to the link of the engine stop switch and the coil of the starter relay.

I suppose that one could fashion a Ballast Resistor out of high temperature resistors, possibly those 10Amp 1- 20 ohm sand cast resistors that can be bought at radio shack. However, I do not know if they,(Yamaha's)are critical type fusible resistors designed to blow if too much amperage is put across them so that it protects the TCI as well as dropping the voltage to protect the TCI and coils.

I have not trace them out specifically but I suspect that they make it back to the TCI via a bridge connector in the wiring harness.

[oldyam80sg]

Thanks- I will look at the harness closely again.I got it a year ago and it is also missing the wires for the coils.I don't know why anyone would remove them but it has given me a headache.

[dbeardslee]

Oldyam - if you need a ballast resistor I've got one off a '79 standard you can have. I bypassed it when I put the Mikes XS coils on so it's just taking up space in my parts bin.

[John]

Originally posted by oldyam80sg
Thanks- I will look at the harness closely again.I got it a year ago and it is also missing the wires for the coils.I don't know why anyone would remove them but it has given me a headache.

The 81 model did not use a resistor, so you may have a harness from an 81. There would be no r/w wire for the resistor in the harness. The r/w will go from the TCI to the coils.

[oldyam80sg]

John- I looked at the harness.It says part #4RO and a whole bunch of numbers.Didn't they make a 4RO unit similar to the TCI unit that i have on my SG?I have a ballast resistor but could this unit be wired to fit? If not i will search again for another harness.

[John]

4R0 is the P/N for anything 81SH related. You definitly have an 81 Special harness. The 81 also used a different TCI than the 78-80. I don't know if the pin-out of the 4R0 TCI is the same as a 2H7 TCI. Randy Rago might know, try asking him, or just look at what color wires are in what position in the connectors. The terminals can be removed from the connector and placed in the correct position.
If you have a 4R0 TCI, then you will need the pick up coil/vac advance/governor assembly from an 81 also, but you'll need to use 81 (3ohm) or newer coils if you do that.
You could cut the r/w wire to the coils and run it to the resistor if you want to use the 4R0 harness.

[oldyam80sg]

I looked at the connectors.Everything appears to match except that there is no red/white wires and there are no wires for the coils either.I'm in desperate need of a harness because i cant get the headlights,turn signals,oil pressure light, or lights inside the gauges working.I spent 2 hours unplugging wires and nothing.The only light that works is the neutral light and the tach works.

[John]

Check the blue wire coming from the ignition switch for the lighting problem. The brown wire from the ign switch powers up all of the fuses except the main fuse. The red wire going to the ign switch is from the main fuse, and it powers up everything that the blue and brown wires connect to. If there is no power to the blue or brown wire, but the red wire has power, then your ign switch may be at fault.

[oldyam80sg]

John- I see a blue connector,a red connector and a brown connector,but what goes in them? Everything else is plugged in but these 3 connectors are empty.I see nothing that is not connected.

[John]

You'll need to open up the headlight bucket, and check at the plug for the ign switch. There may be three or four wires in the plug. You should have four. They are red, blue, brown, and a color that I can identify in the schematic.
There will be empty terminals in the bucket that are for accessories.

[oldyam80sg]

I opened headlight bucket and looked at all connectors-Is there a ground that is supposed to be connected according to the diagram?If so approximately where up by the headlight should this be-Anyone?

[John]

The only grounds in the bucket will be on the turn signal stems. There may be some empty ground connectors in the bucket, but most of the ground wires in the harness terminate at the rear screw that secures the voltage regulator to the frame.

[oldyam80sg]

John- I will check that tomorrow.Thank You for all your help.

[John]

Did you ever sort it out?