1. Kick-start mechanism issue: Inspect the kick-start mechanism to ensure it's engaging properly. Check for any worn or damaged parts, especially the kick-start gear, kick-start shaft, and the one-way clutch.
2. Faulty ignition coil: The ignition coil is responsible for generating the necessary voltage for the spark plug. Check the ignition coil's wiring and connections. Test the ignition coil using an ohmmeter to see if its resistance values are within specifications.
3. Spark plug: Ensure the spark plug is clean, properly gapped, and in good condition. A worn-out spark plug can cause intermittent or no spark.
4. CDI (Capacitor Discharge Ignition) unit: The CDI unit controls the timing and release of the electrical current needed for the spark plug. Check the CDI unit's connections and test it according to the manufacturer's specifications.
5. Wiring and connections: Inspect the entire electrical system, especially the wiring related to the ignition circuit, for any loose connections, breaks, or damage. Poor electrical connections can cause intermittent spark or no spark at all.
6. Kill switch: Make sure the kill switch is functioning correctly and not causing an interruption in the ignition circuit.
7. Stator: The stator generates electricity for the ignition system. Check the stator's resistance values using a multimeter to make sure they're within specifications.
8. Bad ground: Make sure the engine has a good grounding connection to the frame.
If you lack the necessary tools or expertise to perform these checks and tests, it's best to take your KTM 125 to a qualified motorcycle mechanic for an accurate diagnosis and repair.
