There are three ignition generations in the brief, and they are not a set of interchangeable black boxes. This page names them, says what owners already report, and stops where a pinout would have to be invented. A redrawn diagram is future work. It is not in this edition.

SEM, Nippondenso, EFI Technology

The Rotax 123 uses SEM ignition. The stator is the part the brief says is hard to find. If you are buying a 123 project, treat the stator as a scarce part. No price is recorded here.

The Rotax 122 uses a Nippondenso CDI through the bee-tail and the RSV-style bikes. The brief describes an “environmental” retard around 5–6,000 rpm. The derestriction steps say that retard can be removed, and they also say the detail varies by unit, so verify it per model. This guide does not publish a wire colour or a solder bridge. A wrong bridge on a CDI is a dead ignition, and the colours are To verify on the unit in your hand against a manual for that part number.

The Euro 3 bike, RD and RM, uses a combined ECU from EFI Technology. It is not a Nippondenso CDI with a different sticker. It reads the throttle-position sensor, the carburettor heater, air temperature and the extra-air system. Hartrusion, via the brief, rates the TPS ignition well and the generation is also called fussy. Diagnose the sensors before you condemn the ECU. Voltages are To verify.

The four-stroke RS4 and RS 125 are fuel injected and their ignition is not described in the brief. To verify in the manual for that bike. Do not fit a two-stroke CDI to one.

What you can check without a diagram

These checks are general workshop practice. They do not depend on a colour code.

1. Battery voltage, key off and key on. The brief does not give a minimum. A battery that falls over when the headlight is on will pretend to be a CDI fault. The pass voltage is To verify.
2. Earths. A dirty engine earth makes every sensor lie. Clean the earth you can see, and find the others from the manual rather than adding random wires.
3. Connector latches and green corrosion, especially under the tank and at the tail, where water sits.
4. Spark, with the plug body earthed to the head, using a plug you are prepared to replace. Hold the cap with insulated pliers. A visible spark is not proof of spark under compression. It does prove the coil is not open-circuit.
5. Continuity of the one wire you have identified from the manual, not of “the green one” from memory.

The brief lists “coil damp” among the topics for this guide. That is likely the suppression on the coil or the cap. The resistance is To verify. Do not replace a cap with a random resistor plug cap and expect the same CDI to be happy.

Immobiliser

On the RSV-style generation, owners report trouble with the factory immobiliser and alarm. The brief records the complaint and not the cure. There is no bypass on this page. If a PY cranks and does not start, or does not crank, include the immobiliser in the list with the side stand, the kill switch and the CDI. Transponder keys and coded units are a dealer or a specialist job when the manual’s procedure is exhausted.

Loom repairs

Solder and heat-shrink a broken wire once you know what it is. Do not twist and tape it. Do not add scotch-locks in the steering head, where the loom flexes. If you do not know what the wire is, leave it and get the diagram. A wiring diagram redrawn for this site is one of the later downloads in the plan. Until it exists, the official diagram is the source, and any colour called out from memory is To verify.