One of the most frustrating problems you can run into with a GY6-powered go-kart, scooter, buggy, or ATV is when the engine turns over—but won’t spark. A no-spark issue means the engine is completely dead in the water, but the good news is: most causes are predictable, and there’s a straightforward way to track them down.
Let’s walk through a methodical approach to diagnose and fix the problem without guesswork or wasted time.
⚠️ What Does “No Spark” Actually Mean?
Before you begin, confirm it’s actually a no spark issue. Remove the spark plug, reconnect it to the coil wire, and hold the plug’s metal base against clean metal on the engine (use insulated gloves). Crank the engine. If there's no blue spark jumping the gap, you're in the right place.
🔌 Step 1: Rule Out Safety & Kill Switches
The GY6 ignition system is independent of the battery but depends on the CDI (Capacitor Discharge Ignition) to receive uninterrupted power. Many machines have safety features like:
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Handlebar kill switches
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Brake safety switches
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Kickstand cutoffs
These can silently cut off spark if they’re faulty. As a first test, unplug the kill switch wire (usually a black/yellow or black/white wire) from the CDI. Then crank again. If spark returns, one of those switches is the culprit.
⚡ Step 2: Test the Stator Output
The stator generates AC voltage to power the CDI. You’ll need a multimeter set to AC voltage.
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Disconnect the stator from the CDI.
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Crank the engine.
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Check the power source coil (often red/black wire) for 50–100V AC.
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Check the trigger coil (usually blue/white wire) for 0.2–0.8V AC.
If these readings are low or missing, the stator is likely failing or misaligned under the flywheel.
📦 Step 3: CDI (Ignition Box) Functionality
The CDI receives input from the stator and sends a timed pulse to the ignition coil. If the stator checks out but you’re not getting a spark at the plug, the CDI may be bad.
How to test:
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If you have a known good CDI, swap it in.
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Alternatively, measure AC voltage leaving the CDI to the ignition coil. If there’s nothing, the CDI isn’t firing.
Note: CDI failure is common after stator damage or jump-starting with the wrong polarity.
🔁 Step 4: Check the Ignition Coil and Plug Wire
The coil amplifies voltage to create a spark. To test:
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Measure resistance across the primary coil (input terminals): around 0.1–1.0 ohms.
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Measure resistance from plug boot to ground (secondary winding): 3k–10k ohms.
Anything outside these ranges means the coil is suspect. Also inspect the spark plug cap and wire for cracks or corrosion.
🔥 Step 5: Inspect the Spark Plug
It seems obvious, but spark plugs do fail. Make sure:
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The electrode isn’t fouled, bent, or cracked.
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The gap is correct (usually 0.6–0.7mm for GY6).
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Swap in a known good plug as a final test.
🧩 Bonus Tips: When the Basics Don’t Work
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Bad grounds: Ensure the engine has a clean ground connection to the frame and the CDI.
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Loose or corroded connectors: Re-seat every plug in the ignition system.
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Wrong or mismatched parts: GY6 CDIs come in AC and DC versions. Using the wrong type will give you no spark.
🧠 Wrap-Up: Simplified Troubleshooting Flow
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Unplug kill switch → check spark
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Test stator output → good voltage?
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Check CDI → try a known good one
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Test ignition coil → confirm resistance
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Check/replace plug → still no spark? Re-check everything.
A no-spark condition might feel overwhelming, but a step-by-step plan makes it manageable. If you're still stuck, take photos of your wiring and setup—sometimes a fresh set of eyes can spot something you've overlooked.