YAMAHA ROCKER SCREW 67D-12157-00 PA166F-010008

Function and technical context

This rocker arm bolt is a critical structural element of the timing system on Yamaha four-stroke engines, responsible for securing the rocker arm to the camshaft. The rocker arm transmits the rotary movement of the camshaft to the intake and exhaust valves, allowing their opening and closing synchronized with the engine's combustion cycle. A defective or insufficiently tightened screw in this area causes misalignment in the distribution, generating compression leaks, progressive loss of power and, in the most serious cases, destructive contact between valves and pistons that compromises the integrity of the engine.

When to replace this part?

Characteristic symptoms of deterioration include audible metallic noises from the cylinder head (rocker arm rattling), abnormal vibration at idle, difficulty starting due to loss of compression, and oil leaks around the cylinder head. Although the rocker arm screws have considerable durability, it is advisable to check their condition and check their tightness during each seasonal maintenance, especially after cleaning or valve adjustment operations. Preventative replacement of this screw during a scheduled timing overhaul prevents emergency boating repairs and prolongs the life of the timing assembly.

Equivalent manufacturer part numbers