If you have replaced all the components that could potentially be causing the issue, and your motorcycle still won't start, there might be some additional factors to consider. Here are a few possible reasons:
Electrical system: Check the battery and connections to ensure they are in good condition and properly connected. Faulty wiring, loose connections, or a malfunctioning ignition switch could prevent the motorcycle from starting.
Fuel delivery: Verify that fuel is reaching the engine by checking the fuel pump, fuel lines, and fuel filter. A clogged fuel line or a malfunctioning fuel pump can hinder the proper flow of fuel to the engine, resulting in a no-start situation.
Ignition system: Inspect the ignition coil, spark plugs, and spark plug wires for any faults. A faulty ignition coil or worn-out spark plugs may prevent the engine from starting.
Engine compression: Low or no compression in the cylinders can make starting difficult. Perform a compression test to determine if the engine's compression is within the manufacturer's specified range.
Safety switches: Many motorcycles have safety switches such as a side stand switch or a clutch switch that prevent the engine from starting if not in the correct position. Check these switches to ensure they are functioning properly.
Engine timing: Incorrect ignition timing can prevent the engine from starting. Verify that the timing is set correctly according to the manufacturer's specifications.
ECU or ECM issues: If your motorcycle has an Engine Control Unit (ECU) or Engine Control Module (ECM), there might be a problem with its functionality. It's worth checking if there are any error codes stored in the ECU or ECM that could provide additional insight into the problem.
Mechanical issues: Despite having replaced several components, there might still be an underlying mechanical problem, such as a seized engine, damaged valves, or a broken camshaft. A thorough inspection by a qualified mechanic can help identify such issues.
Remember, troubleshooting a motorcycle's starting problem can be complex, and it's often best to seek the assistance of a professional mechanic who has experience with your specific motorcycle model. They will have the necessary tools and expertise to diagnose and address the issue effectively.