What Causes Abnormal Noises When Starting a Motorcycle?
1 Answers
Abnormal noises when starting a motorcycle may include air leakage sounds, valve tapping sounds, or piston ring noises. Air Leakage Sound: If the fastening bolts between the cylinder and cylinder head, cylinder and crankcase, or left and right crankcases are loose or the gasket is damaged, a hissing air leakage sound may occur. The sound is difficult to hear clearly during steady operation after starting. During a stationary inspection, obvious oil traces can be found at the leakage point. If the issue is not severe, simply tightening the fastening bolts may suffice. In severe cases, replacing the gasket is necessary. Valve Tapping Sound: If the valve clearance becomes too large due to improper adjustment or part wear, the valve mechanism will produce short, sharp tapping sounds. This tapping does not vary with changes in engine speed. The issue can be resolved by adjusting the valve clearance or replacing worn parts. Piston Ring Noise: If the piston rings are worn, lack sufficient tension, are stuck, or have excessive end gap, side clearance, or back clearance, combustion gases will rapidly leak into the crankcase during engine operation, producing a leakage knocking sound. By placing a screwdriver against the spark plug and listening carefully, distinct popping sounds can be heard.
