There could be several reasons why a motorcycle engine might shut off at high speeds. Here are a few possible causes:
Fuel Delivery Issues: Insufficient fuel supply or a clogged fuel line can cause the engine to shut off. At high speeds, the engine demands a higher fuel flow rate, and any restriction in the fuel system can lead to fuel starvation and engine stalling.
Ignition System Problems: Faulty ignition components such as spark plugs, ignition coils, or the ignition control module can result in intermittent or complete loss of spark. Without a spark, the fuel-air mixture cannot ignite, causing the engine to shut off.
Electrical Malfunction: A problem with the electrical system, such as a loose or damaged connection, faulty wiring, or a malfunctioning sensor, can lead to an engine shutdown. High-speed vibrations and increased electrical load at higher RPMs can exacerbate these issues.
Overheating: If the engine is not properly cooled, it may overheat during high-speed riding. Overheating can cause the engine to shut off as a protective measure. Insufficient coolant, a malfunctioning thermostat, or a faulty cooling fan can contribute to overheating.
Air Intake Issues: A restricted or blocked air intake can disrupt the air-fuel mixture ratio, leading to engine stalling. This can occur due to a clogged air filter, a malfunctioning throttle position sensor, or an issue with the intake manifold.
Mechanical Problems: Mechanical issues within the engine, such as a seized or damaged component, can cause the engine to abruptly shut off. These problems might include a broken camshaft, a malfunctioning valve, or a damaged piston.
ECU or ECM Malfunction: The Engine Control Unit (ECU) or Electronic Control Module (ECM) is responsible for managing various engine functions. If the ECU or ECM malfunctions or experiences a software glitch, it can cause the engine to shut off unexpectedly.
It's important to note that diagnosing the exact cause of an engine shutdown requires a thorough inspection and potentially the expertise of a trained mechanic. If you're experiencing frequent engine shutdowns at high speeds, it's recommended to have your motorcycle inspected by a professional to determine and resolve the underlying issue.