REF: Electrical System

Ironhead - Simplified Wiring Schematics

This wiring diagram is a minimal config - No Starter - No Turn Signals - No Front Brake Switch - No Kill Switch.

The ignition module is an Ultima Single-Fire version, feeding separate trigger signals to the dual coils to fire the front & rear spark plugs separately. It fits in the nosecone where previously only the cam sensor plate mounted. A dual-fire version of the Ultima ignition could be used instead, with the appropriate dual-fire coil. Using the VOES connection (which helps with idle & cruising spark timing by providing more advance) is recommended, but implementing a tachometer is optional.

There are only six wire colors to minimize wire purchase: Black - White - Red - Blue - Yellow - Green. There are enough colors so that no connecting point should have the same color twice in order to make it easier to know which device is connected to/from another device.

This circuit uses the Frame/Engine for ground conduction. Be sure you have good ground points at the needed locations or run a separate black wire to those locations to assure a good ground.

Beware that the brake light shares the same fuse as the ignition circuit - So, if you have a short to ground in the brake circuit it will blow the fuse & kill the ignition. You could add a separate fuse for the brake light to avoid that potential problem.

The diagram shows an optional Gen Light, implemented with a diode and an incandescent bulb.

To implement the VOES, add it with a vacuum hose to the carb - then wire the single VOES wire into the Violet Wire of the Ultima ignition module.

To implement a tachometer, use a normal HD dual-fire tach and wire the input signal to the Green Wire of the Ultima module.

Some Other Simplfied Wiring Diagrams to represent basic wiring:

Wiring for Magneto Fired Sportsters 1)


Wiring for an Electric Start Sportster 2)


Generic HD Wiring Diagram 3)


Ironhead CAD Wiring Diagram ('77) 4)


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