1. Differences in air/fuel mixture: It's possible that the rear cylinder is getting a richer air/fuel mixture than the front cylinder. This could be due to a number of factors, such as a clogged or damaged fuel injector, a vacuum leak, or a problem with the carburetor (if the bike is carbureted).
2. Differences in ignition timing: The rear cylinder may also be firing at a different time than the front cylinder. This could be due to a problem with the ignition coil, spark plug wire, or distributor cap.
3. Differences in exhaust flow: The rear cylinder may also have a more restrictive exhaust system than the front cylinder. This could be due to a clogged or damaged exhaust pipe, muffler, or catalytic converter.
4. Differences in engine temperature: The rear cylinder may also be running hotter than the front cylinder. This could be due to a problem with the cooling system, such as a clogged radiator or water pump.
Any of these issues can cause the rear cylinder plug to foul quickly, even if the bike is running too rich. If you're experiencing this problem, it's important to have the bike inspected by a qualified mechanic to determine the cause and get it fixed.
