There could be several reasons why your new bike engine is overheating after a 12 km ride. Here are some possible explanations:
Insufficient cooling: The engine may not be getting enough cooling due to a malfunctioning or blocked cooling system. Check if the radiator is clogged, the coolant level is adequate, and the fan is functioning properly.
Cooling system leak: There could be a leak in the cooling system, leading to a loss of coolant. Inspect the hoses, radiator, and water pump for any signs of leakage.
Incorrect fuel mixture: If the fuel mixture is too lean (not enough fuel) or too rich (too much fuel), it can cause the engine to overheat. Ensure that the carburetor or fuel injection system is properly adjusted.
Inadequate lubrication: Insufficient lubrication can cause increased friction and heat buildup in the engine. Check the oil level and quality, and make sure the oil pump is functioning correctly.
Faulty thermostat: The thermostat regulates the engine temperature by controlling the flow of coolant. If it is stuck closed or open, it can lead to overheating. Have the thermostat checked and replaced if necessary.
Improper break-in period: If the bike is new, it's important to follow the manufacturer's recommended break-in procedures. Failure to do so can cause the engine to overheat during the initial rides.
Blocked air intake: A blocked air intake can restrict airflow to the engine, causing it to overheat. Check the air filter and ensure it is clean and not obstructed.
Malfunctioning water pump: The water pump circulates the coolant through the engine. A faulty water pump can result in inadequate coolant flow and overheating. Inspect the pump for any issues.
If you've checked these potential causes and are still experiencing overheating, it is advisable to consult a professional mechanic or take your bike to an authorized service center. They will have the expertise to diagnose and resolve the issue effectively.