A tappet noise in a motorcycle engine, often referred to as a "ticking" or "clicking" sound, is typically associated with the valvetrain. The valvetrain consists of components such as the camshafts, valves, lifters (tappets), pushrods (in some engine configurations), and associated springs and retainers. Here are some common causes of tappet noise in motorcycles:
Valve Clearance: Each valve in the engine is designed to operate within a specific clearance range. Over time, as the engine wears and components settle, the valve clearance may become too tight or too loose. When the clearance is too tight, the valve may not fully close, causing it to make contact with the tappet or other valvetrain components. This contact produces the ticking sound. Adjusting the valve clearance to the manufacturer's specifications can often resolve this issue.
Worn Valvetrain Components: The valvetrain components, such as the camshaft lobes and lifters (tappets), can wear over time due to normal use and engine operation. Excessive wear can lead to increased clearance between the camshaft lobes and lifters, causing noise during valve operation. In such cases, replacing the worn components may be necessary to eliminate the noise.
Lifter (Tappet) Issues: Lifters or tappets can experience problems that contribute to noise. In hydraulic lifters, for example, the internal mechanisms, such as the plunger or check valve, may become worn or damaged, resulting in inadequate hydraulic pressure. This can lead to excessive clearance between the lifter and camshaft, causing noise. Replacing or rebuilding the lifters can address this issue.
Improper Lubrication: Adequate lubrication is crucial for the smooth operation of the valvetrain components. Insufficient or degraded engine oil can cause increased friction and wear, leading to tappet noise. Regular oil changes with the manufacturer-recommended oil and proper oil level maintenance can help prevent this problem.
Engine Temperature: Tappet noise can sometimes be more noticeable when the engine is cold. As the engine warms up, the metal components expand, and the noise may diminish or disappear. However, if the noise persists even when the engine is fully warmed up, it could indicate an underlying issue that requires attention.
If you're experiencing tappet noise in your motorcycle, it is recommended to have a qualified mechanic or technician inspect the engine. They can diagnose the specific cause of the noise and perform any necessary repairs or adjustments to restore proper operation and reduce or eliminate the tappet noise.