No Spark? Check These Things Before Replacing the Ignition Coil

No spark problems are common on 2-stroke machines.

Many people replace the spark plug first. If that does not work, they often replace the ignition coil next.

In many cases, the ignition coil is not faulty.

Before replacing parts, work through these checks.

Quick Ignition System Check

1. Check the Spark Plug

Remove the spark plug and inspect it.

• Check for damage or heavy fouling
• Check the electrode gap
• Look for cracked ceramic insulation
• Test with a known good plug if possible

2. Use a Spark Tester

A spark tester confirms whether the ignition system is producing spark.

• Connect the tester between the HT lead and spark plug
• Pull the starter cord
• Look for a strong blue spark

A weak yellow spark can indicate ignition problems, poor grounding or a failing coil.

3. Check the Stop Switch

A faulty stop switch or damaged wire is one of the most common causes of no spark.

• Move the switch to the RUN or ON position
• Disconnect the kill switch wire from the ignition coil
• Test for spark again

If spark returns, the fault is likely with the switch or wiring.

4. Inspect the HT Lead and Spark Plug Cap

The HT lead carries high voltage from the ignition coil to the spark plug.

• Check for cuts, cracks or burns
• Make sure the lead is secure in the ignition coil
• Inspect the spark plug cap for corrosion or looseness
• Ensure the internal clip grips the spark plug firmly

5. Check the Flywheel and Coil Gap

The ignition coil must sit at the correct distance from the flywheel magnets.

• Remove dirt, rust and debris from the flywheel area
• Inspect the flywheel magnets for damage
• Check the air gap between the flywheel and coil
• Most 2-stroke machines use a gap around 0.25 mm to 0.40 mm

A business card is commonly used as a simple gap setting tool.

6. Check for Loose or Damaged Wiring

Vibration and heat can damage ignition wiring over time.

• Inspect all visible wires
• Look for trapped or rubbed-through insulation
• Check connectors for corrosion
• Ensure all mounting screws are tight

Common Mistakes to Avoid

• Replacing the ignition coil without testing the stop switch
• Assuming a new spark plug is definitely good
• Setting the coil gap incorrectly
• Leaving corrosion on the flywheel magnets
• Ignoring damaged wiring near the handle or engine housing

When the Ignition Coil Is Faulty

Ignition coils do fail, but usually after other causes have been ruled out.

Common signs include:

• No spark after isolating the stop switch
• Weak spark when the engine is hot
• Machine starts cold but cuts out after warming up
• Intermittent spark during operation
• Visible cracking or heat damage on the coil body

Heat-related failure is common. Some ignition coils work when cold, then fail once engine temperature rises. The machine may restart after cooling down.

Before Ordering a New Ignition Coil

• Check the machine model number
• Match the correct part number
• Compare wiring and connector layout
• Inspect the flywheel magnets before fitting a new coil

Using the wrong ignition coil can cause poor running or complete loss of spark.

Need Help Finding the Correct Part?

We stock ignition coils, spark plugs, HT leads, spark plug caps and ignition parts for many popular 2-stroke machines used in the UK.

If you are unsure which part you need, contact our team with the machine model details.

Email: sales@lsengineers.co.uk