How To Test 2 Stroke Cdi With Pickup -stator

How to Test a 2-Stroke CDI with Pickup Coil/Stator

Testing a CDI (Capacitor Discharge Ignition) unit on a 2-stroke engine, along with its associated pickup coil or stator, can seem daunting, but with the right approach and tools, it’s a manageable task. This guide walks you through the process, helping you diagnose whether your CDI or pickup coil is the source of your engine's ignition problems.

Understanding the System: CDI and Pickup Coil Interaction

Before diving into the testing, it's crucial to grasp the basic functionality. The pickup coil (or stator) acts as a sensor, detecting the engine's crankshaft position. It generates a weak signal as the flywheel rotates, indicating the precise moment to fire the spark plug. This signal is then sent to the CDI unit. The CDI amplifies this weak signal, creating a high-voltage pulse that's powerful enough to ignite the spark plug. If either the pickup coil or the CDI malfunctions, your engine won't ignite properly.

Tools You'll Need

• Multimeter: Essential for checking continuity, resistance, and voltage. A digital multimeter is preferred for accuracy.
• Ohmmeter (part of most multimeters): To measure the resistance of the pickup coil and CDI components.
• Spark Tester: To verify that the CDI is producing a strong spark. A simple inductive spark tester is sufficient.
• Wiring Diagram: Specific to your engine model. This is vital for identifying correct wire connections and component locations. Without the correct wiring diagram, testing is extremely difficult and may lead to inaccurate results.
• Screwdrivers: For accessing the components.

Testing the Pickup Coil/Stator

1. Visual Inspection: Start with a thorough visual inspection of the pickup coil for any obvious damage, such as broken wires, melted insulation, or cracks in the coil itself.

2. Resistance Test: Using your ohmmeter, measure the resistance of the pickup coil. Your engine's service manual will provide the specified resistance values. Deviations from the specified values indicate a problem with the pickup coil. Keep in mind there are typically multiple windings in the stator. Your manual will guide you on testing each one.

3. Continuity Test: Check the continuity of the pickup coil wires. The wires should show continuity, indicating a complete circuit. Lack of continuity suggests a broken wire.

Testing the CDI Unit

Testing the CDI directly is more challenging and often requires specialized equipment. However, you can perform some basic checks:

1. Visual Inspection: Inspect the CDI unit for any physical damage, such as cracks, burns, or loose connections.

2. Power Supply Test (if possible): Using a 12V power supply (with care!), and following the relevant wiring from your manual, you may be able to see if the CDI unit outputs a voltage spike when a weak pulse is simulated to its input. This test is highly model dependent and may not be feasible on all systems without access to specialized equipment or a specific triggering signal generator.

3. Spark Test (Indirect CDI test): The most effective method to check the CDI is to check for spark. With the pickup coil confirmed to be working, connect the CDI and spark plug wire, then crank the engine. If no spark is present, the CDI is likely faulty.

Interpreting the Results

• Pickup Coil Failure: Resistance readings outside the specified range, lack of continuity, or physical damage to the pickup coil indicate a fault. Replacement is typically necessary.

• CDI Failure: Absence of spark even with a functional pickup coil strongly suggests a faulty CDI unit. Replacement is usually required.

Important Considerations

• Safety First: Always disconnect the battery before working on any electrical components. High voltage is present in ignition systems.

• Consult Your Service Manual: This is the most critical step. Your engine's service manual provides specific instructions and resistance values for your model. Trying to diagnose without it can be dangerous and ineffective.

• Professional Help: If you're not comfortable working with electrical systems, it's best to seek professional assistance.

By carefully following these steps and consulting your engine's service manual, you can effectively diagnose whether your 2-stroke engine's ignition problems stem from a faulty pickup coil or CDI unit. Remember, safety and accuracy are paramount throughout this process.