There could be several reasons why your dirt bike pulls in neutral but cuts off when in gear. Here are a few possibilities:
Clutch Issues: The most common cause is a problem with the clutch. If your clutch is not fully disengaging when you pull in the clutch lever, it can cause the bike to try to move forward even when in gear. This can result in the engine stalling. Check the clutch cable for proper adjustment and ensure that it is operating smoothly. If the clutch plates are worn or damaged, they may need to be replaced.
Transmission Problems: Issues with the transmission can also cause the bike to cut off in gear. If there are damaged or worn gears or the transmission is not shifting properly, it can lead to the engine stalling. This is a more complex problem and may require professional inspection and repair.
Fuel Delivery Issues: Insufficient fuel supply to the engine can cause stalling. Check if there is enough fuel in the tank and ensure that the fuel lines are clear of any blockages. Additionally, a dirty or clogged fuel filter could restrict the flow of fuel, leading to engine problems.
Carburetor Troubles: If your dirt bike has a carburetor, it may be dirty or require adjustment. A clogged carburetor can disrupt the fuel-air mixture and affect engine performance, particularly when under load. Cleaning or adjusting the carburetor may resolve the issue.
Ignition System Problems: Faulty ignition components such as spark plugs, ignition coils, or the ignition timing can cause the engine to stall. Inspect these parts for any damage or wear and consider replacing them if necessary.
It's important to note that diagnosing and repairing motorcycle issues can be complex, and it may be best to consult a professional mechanic who specializes in dirt bikes for a proper diagnosis and resolution of the problem.