No Spark? Try These Fixes Before Replacing Your Ignition Module

At L&S Engineers, we’ve noticed more customers coming to us with no spark problems on their 2-stroke machines. Often, they’ve already replaced the spark plug—which is a good first step—but when that doesn’t fix the issue, the next move is usually to buy a new ignition module.

However, in most cases, the ignition module isn’t the culprit.

Top 3 Common Misdiagnoses Before Replacing the Ignition Module

1. “The spark plug is new, so the module must be faulty.”
   Even new plugs can be faulty. Always test with a known good plug and a spark tester.
2. “There’s no spark, so the ignition module is dead.”
   Often, a shorted kill switch wire is the real culprit. Disconnect it and test again.
3. “I replaced the module but it still won’t start.”
   If HT leads, spark plug boots, or flywheel gaps aren’t checked, the problem persists despite a new ignition module.

Before you spend money on a new module, here are some other areas to check that could save you time and hassle.

1. Use a Spark Tester

If you’re unsure whether there’s spark, a spark tester is an inexpensive and reliable tool to confirm it.

We recommend the L&S Engineers Spark Tester (part no. 015 800), designed specifically for 2-stroke machines. It’s easy to use and helps take the guesswork out of spark testing.

2. Check the Kill Switch (On/Off Switch)

A faulty or shorted kill switch is one of the most common reasons for no spark.

• Ensure the kill switch is in the ON position.
• Disconnect the kill switch wire from the ignition module.
• Pull the starter cord and check for spark.
• If spark returns, the issue is likely with the switch or wiring, not the ignition module.

3. Isolate the Ignition Module by Disconnecting the Positive Wire

To check if the ignition module is affected by other electrical parts:

• Make sure the kill switch is in the ON position.
• Disconnect the positive wire feeding the ignition module.
• Pull the starter and check for spark.
• If spark is present when isolated, the fault is likely with wiring or switches, not the ignition module.

4. Inspect the HT Lead (High Tension Lead)

The HT lead connects the ignition module to the spark plug boot and carries the high-voltage spark.

• Look out for cracks, brittleness, or exposed wiring.
• Make sure connections at both ends are secure.
• Replace the HT lead if damaged or worn.

5. Check the Spark Plug Boot

The rubber spark plug boot can deteriorate over time.

• Check that the metal clip inside grips the spark plug firmly.
• If the boot is cracked, loose, or damaged, replace it.

6. Clean the Flywheel and Ignition Module Area

Rust, dirt, or oil on the flywheel or ignition module can interfere with spark generation.

• Remove the starter assembly.
• Clean the flywheel and ignition module surfaces thoroughly.
• Check and set the air gap between the flywheel and module to approximately 0.3 mm (refer to your machine’s manual).

When the Ignition Module Is the Problem

Sometimes the ignition module only fails when the machine warms up:

• The engine runs well when cold.
• After a few minutes, it cuts out with no spark.
• It may start again after cooling down.

This heat-related failure is a classic sign the ignition module needs replacing.

Need Help?

If you’ve checked everything and still need assistance, our experienced sales team at L&S Engineers is here to help.

We stock genuine ignition modules and parts compatible with UK machines and can advise on the correct components.

Call us: 01543 378189
Email us: sales@lsengineers.co.uk