CB400A/CM400A/CM450A Hondamatic CDI - Test before installing New CDI

Coil Test:

• Primary Side: Measure the resistance between the Yellow and Green wires. The Yellow and Green wires being measured will be coming out of the spark plug coil. The resistance should be less than 1 Ohm. Spec is 0.35 to 0.55 Ohms.

• Secondary Side: Measure the resistance**Coil Test:**

- **Primary Side:** Measure the resistance between the Yellow and Green wires coming from the spark plug coil. It should be less than 1 Ohm, with a specification of 0.35 to 0.55 Ohms.

- **Secondary Side:** Measure the resistance of the spark plug wires after removing the plug end caps. The spec for stock Honda coils is 7.2K Ohms to 8.8K Ohms, and other coils may have different specifications.

- **Plug End Caps:** Measure the resistance of the plug end caps, which should be around 5K Ohms. The replacement part number is NGK XD05F.

**Stator Tests:**

The connectors can be found under the left side cover.

- Measure the Pink and Green wires in the large 6-pin connector (advance pickup coil): resistance should be between 10 to 30 Ohms.

- Measure the White and Blue wires in the 2-pin connector (power to the CDI): resistance should be between 4 to 7 Ohms.

- Measure the White wire in the 2-pin connector and Green wire in the large 6-pin connector: resistance should be between 200 to 500 Ohms.

- Measure the Brown and Orange wires in the large 6-pin connector (primary pickup coil): resistance should be between 100 to 200 Ohms.

Keep in mind that the stator ohm readings can exceed the old specification by no more than 1 Ohm. If in doubt, verify with a timing light, ensuring timing marks align correctly at various RPMs.

**Change Relay Test:**

Set your Digital Volt Meter (DVM) to Volts. Connect the red probe to the Green wire with a Red tracer in the 2-pin connector, and the black probe to the Green wire in the 3-pin connector. Place the bike in Neutral with the key in the "Run" position.

- In Neutral, expect about 0.7V (for OEM). If you built a relay with a MOSFET or sourced one from me, it may be lower.

- In 1st and 2nd gears, voltage should read 11-13V, matching battery voltage.

**Tip:** If uncertain about the change relay, disconnect the Green wires with Black and White tracers from the sidestand switch. If it sparks, the sidestand switch is defective. You can also disconnect the connectors leading to the change relay from the neutral switch – the starter won’t work, but you can kickstart to verify spark. If it sparks then, the change relay is likely at fault.

**Run/Kill and Ignition Switch Tests:**

Connect one probe to the Black wire with a White tracer from the main wiring harness that connects to the CDI unit, and the other probe to the negative battery terminal.

- With the ignition switch in the "On" position and Run/Kill switch in "Run," expect infinite Ohms (open circuit).

- With the ignition on and Run/Kill in "Off," expect close to 0 Ohms (circuit closed to ground).

- With the ignition switch "Off," Run/Kill in any position should also show close to 0 Ohms.

**Tip:** If unsure about the ignition or kill switch, disconnect the Black wire with a White tracer leading to the CDI. If it starts, the issue lies with the switch.

**Alternator Tests:**

Use the connector with 3 Yellow wires.

- Test each Yellow wire against another; resistance should be below 1 Ohm for each pairing.

- Test each Yellow wire against ground; expect infinite Ohms indicating no shorts.

**Stator Crank and Running Tests with Peak Voltage Adapter (Recommended):**

- Connect probes accordingly as per specifications to check voltage readings at various points during cranking and at idle. Expect certain voltages (e.g., 14 Volts at the Green and White connection when cranking) and progressively increasing readings when throttling.

**Stator Crank and Running Tests with Analog Volt Meter:**

- Follow similar connections and check corresponding voltages at idle to confirm the proper operation of coils, ensuring readings align with the expected performance metrics for low RPM and high RPM coils.

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**Rotor Test:**

Remove the rotor and check the strength of the magnets inside. They should strongly attract small metallic tools. If they do not, the rotor may need replacement.e of the spark plug wires with the plug end caps removed, they unscrew. Insert a probe into each wire. Spec is 7.2K Ohms to 8.8K Ohms for the stock Honda coil, other coils will have different specs.

• Plug End Caps: Measure the resistance of the plug end caps. Spec is 5K Ohms. Replacement part number is NGK XD05F.

IF THE PRIMARY OR SECONDARY IS OPEN THIS MEANS THE IGNITION COIL IS BAD, GET A USED ONE, D ANY COIL OVER 1.0 OHM ON THE PRIMARY WILL CAUSE INCORRECT PILOT MIXTURE AND WILL CUT OUT SPARK AFTER 10 MINUTES OF RIDING. IF PLUG END CAPS READ INFINITY OR THEY ARE NOT CLOSE TO 5K OHMS THE CAPS ARE BAD, GET A NEW NGK XD05F CAP OR AFTERMARKET EQUIVALENT.