1979 Special with Unknown MNS Motor Questions

[79xs1100s]

I have the Resistor bypassed for the Dynas, but I assume that would be the same to go to stock 81 coils. All I did was unplug the old unit and plug in the new one without changing anything.

So now the run down is...

79 Special harness
Bypassed Resistor
3 Ohm Dyna Coils
"81" Vac and Mech timing advance
79 Special Carbs
4RO TCI

Runs Great.

[Dbshea]

I have the Resistor bypassed for the Dynas, but I assume that would be the same to go to stock 81 coils. All I did was unplug the old unit and plug in the new one without changing anything.

So now the run down is...

79 Special harness
Bypassed Resistor
3 Ohm Dyna Coils
"81" Vac and Mech timing advance
79 Special Carbs
4RO TCI

Runs Great.

Good deal. That'll be the same recipe for me. Thanks for the update.

[3Phase]

Y'all are totally overthinking the ignition system, the ballast resistor is used to limit the normal running current going through the stock 1.5 Ohm 1978 to 1980 ignition coils, it's not for the TCI.

If you're using the '78 to '80 coils or some other ~1.5 Ohm coils it doesn't matter which TCI you have -- use the ballast resistor.

If you're using the '81 coils or some other 3 Ohm coils it doesn't matter which TCI you have -- do not use the ballast resistor.

[Dbshea]

Y'all are totally overthinking the ignition system, the ballast resistor is used to limit the normal running current going through the stock 1.5 Ohm 1978 to 1980 ignition coils, it's not for the TCI.

If you're using the '78 to '80 coils or some other ~1.5 Ohm coils it doesn't matter which TCI you have -- use the ballast resistor.

If you're using the '81 coils or some other 3 Ohm coils it doesn't matter which TCI you have -- do not use the ballast resistor.

Correct. We're on the same page about the ballast resistor and it's lack of association with the ignition unit. Coils need to match the ballast resistor, advance needs to match cams (as closely as possible in some cases) and the tci needs to match the advance. My biggest concern with the swap hasn't been components, it's been wiring. With only the one red/white coming out of the 4RO tci (and not having an 81 diagram to eyeball) I was afraid that circuit would feed the ballast circuit and not directly to the coils. Seems to be unfounded, which is good.

[3Phase]

You got it, no problems.

For just about any conventional ignition, not just the XS11, don't use low-resistance coils with no ballast unless it was designed that way, it burns the ignition points or cooks the transistors.