5-Pin CDI Wiring Diagram

5-Pin CDI Wiring Diagram — interactive diagram. Open it in the editor to customise components and wiring.

This is a free printable 5 pin cdi wiring diagram: download the diagram as SVG or open it and print to paper or PDF.

The Capacitor Discharge Ignition (CDI) unit fires the spark plug at precisely the right moment in the engine cycle. This guide explains each pin on the standard 5-pin CDI connector and how to wire it correctly for reliable ignition.

Capacitor Discharge Ignition (CDI) systems replace older points-and-condenser ignitions with an electronic module that delivers a fast, high-voltage spark. The CDI unit contains a storage capacitor that charges to 200-300 V DC from the source coil (magneto alternator). When the trigger coil detects the correct crankshaft position, it sends a small signal to a silicon-controlled rectifier (SCR) inside the CDI, which dumps the capacitor charge through the ignition coil primary in microseconds. This rapid voltage rise in the primary induces a 20,000-40,000 V pulse in the secondary, which fires the spark plug. The standard 5-pin CDI connector carries these signals on five wires. Pin 1 (AC power from source coil -- typically white/yellow) supplies the charging voltage to the CDI capacitor. Pin 2 (trigger/pickup signal -- typically white/green or orange) carries the timing pulse from the magneto trigger coil. Pin 3 (kill/ground -- typically black/white) grounds the CDI circuit to kill the engine when shorted by the kill switch. Pin 4 (ignition coil output -- typically black or orange) sends the fired high-voltage pulse to the coil primary. Pin 5 (ground -- black) is the main CDI chassis ground. Wiring errors are a common cause of no-spark conditions. Reversed kill-switch wiring prevents the engine from starting if the kill circuit is shorted at rest. Using the wrong source coil connector causes the CDI to charge incorrectly, producing a weak or absent spark. Always measure source coil output with a multimeter in AC voltage mode while cranking -- a healthy source coil delivers 50-200 VAC. Trigger coil output should read 0.5-5 VAC at cranking speed.

A 5 pin CDI wiring diagram covers the standard configuration used on many small motorcycles and scooters, but some aftermarket and performance CDI units — including certain Power Max CDI modules — use a 6 pin connector with an extra terminal for DC power input or a kill-switch signal. A wiring diagram for a Power Max CDI 6 pin unit is frequently needed when swapping to a performance ignition on bikes that originally ran a 5 pin unit, since the additional sixth pin must be correctly identified to avoid a no-spark condition. Use the free online diagram maker to document your CDI wiring before making any changes.

How to wire 5 pin cdi wiring diagram

Identify all connector wires Obtain the wiring diagram for your specific bike. Lay out the CDI connector and identify Pin 1 (source), Pin 2 (trigger), Pin 3 (kill), Pin 4 (coil out), Pin 5 (ground) using the diagram.
Test source coil Connect multimeter to Pin 1 and Pin 5. Kick-start the engine and read AC voltage. Should read 50-200 VAC. Record the value.
Test trigger coil Move meter to Pin 2 and Pin 5. Kick-start and read AC voltage. Should read 0.5-5 VAC. If zero, trigger coil or wiring is faulty.
Verify ground connection Use the meter in resistance mode. Measure from Pin 5 to engine/frame ground. Should read less than 1 ohm. Clean contact point if resistance is higher.
Connect CDI and test spark Connect all five pins. Attach a spark tester to the spark plug cap. Kick-start and verify consistent blue spark at the tester. Orange or weak spark indicates low capacitor output.

Specifications

Source coil output (AC)	50-200 VAC at cranking speed
Trigger coil output (AC)	0.5-5 VAC at cranking speed
CDI capacitor voltage	200-300 VDC (charged)
Ignition coil secondary output	20,000-40,000 V
Kill switch resistance (RUN)	Open circuit (>1 Megohm)

Safety warnings

The CDI output to the ignition coil carries 200-300 V peak -- do not touch coil terminals or spark plug wire during cranking.
Never run the engine with the spark plug cap disconnected -- the open-circuit high voltage can puncture and permanently damage the ignition coil.
Ensure the CDI ground wire makes solid contact to the frame -- a poor ground causes erratic sparking and potential CDI damage.

Tools needed

Digital multimeter with AC and DC voltage ranges
Spark plug tester (neon gap type for safe observation)
Wiring diagram for the specific motorcycle model and year
Electrical contact cleaner for CDI connector pins

Common mistakes

Swapping the source coil and trigger coil wires -- both look similar but carry very different signals; swapping them results in no spark and can damage the CDI.
Leaving the kill switch wire disconnected -- the kill switch grounds the CDI circuit; if left open the engine may not start on some CDI designs.
Using a CDI unit from a different engine displacement -- CDI timing is calibrated for a specific engine RPM curve; mismatched CDIs advance or retard timing incorrectly.

Troubleshooting

No spark at all: Cause: No source coil voltage, failed CDI, or broken kill switch ground permanently grounding CDI Fix: Test source coil VAC during cranking. If present, disconnect kill switch wire from CDI and retest spark. If still no spark with correct source voltage, replace CDI unit.
Weak or intermittent spark: Cause: Weak source coil (low VAC output), corroded CDI connector pins, or failing capacitor Fix: Clean CDI connector pins with contact cleaner. Measure source coil VAC -- if below 50 V, replace source coil. Replace CDI if coil output is correct.
Engine runs but backfires constantly: Cause: CDI timing incorrect (wrong CDI unit) or trigger coil air gap too large Fix: Verify CDI part number matches engine model. Check trigger coil air gap (typically 0.3-0.5 mm). Adjust or replace as needed.

Frequently asked questions

How do I test my CDI unit?

Disconnect the CDI and measure source coil output: AC voltage across the source coil leads while kick-starting. Expect 50-200 VAC. Measure trigger coil output: 0.5-5 VAC during cranking. If coil outputs are correct but there is still no spark, the CDI unit itself is likely faulty. Swap with a known-good CDI to confirm before purchasing a new unit.

Can I use a universal CDI on my motorcycle?

Universal CDIs work on many bikes but must be matched to source coil frequency and timing advance curve. A CDI from a 50cc engine will not produce correct timing on a 125cc engine. Check compatibility using the bike CC rating, engine type (2-stroke vs. 4-stroke), and source coil polarity (DC-powered CDI vs. AC-powered CDI). Incorrect timing burns pistons or prevents starting.

What is the difference between AC CDI and DC CDI?

AC CDI charges its capacitor directly from the magneto source coil alternating current -- common on smaller off-road bikes without a battery. DC CDI uses a DC-to-DC converter to charge the capacitor from the 12 V battery -- found on street bikes with batteries. DC CDI provides more consistent spark at low RPM because battery voltage is stable, while AC CDI spark energy varies with engine speed.

Why does my engine start but die at high RPM?

High-RPM cut-out on a CDI system is most commonly caused by a weak source coil output (insulation breakdown at high temperatures), a failing CDI capacitor that cannot hold charge at high pulse rates, or a resistive connection that drops voltage under load. Measure source coil resistance (should be within specification on the service manual) and inspect all ground connections for resistance.

How do I bypass the kill switch to test for spark?

Locate the kill switch wire (usually black/white) at the CDI connector. Disconnect it from the CDI -- this removes the ground signal. Attempt to start the engine. If spark returns, the kill switch or its wiring has an internal short to ground. Check the kill switch contact resistance with a multimeter in continuity mode -- it should be open when in the RUN position.

What does a wiring diagram for a Power Max CDI 6 pin show compared to a 5 pin CDI?

A Power Max CDI 6 pin wiring diagram typically shows the same core signals as a 5 pin unit — AC power from the exciter coil, a pickup/trigger pulse from the pulser coil, ground, and the kill-switch signal — with a sixth pin that is commonly a second AC power input or a DC supply from the battery/rectifier, depending on the model variant. Because there is no single universal standard for aftermarket 6 pin CDIs, the exact function of each pin should be confirmed against the documentation supplied with that specific unit before connecting. Incorrect wiring, especially swapping the exciter and battery supply pins, can damage the CDI.