BOLT CYLINDER HEAD ORIGINAL YAMAHA 90105-09005

Function and technical context

This cylinder head bolt is an original factory replacement for Yamaha engines that is part of the sealing and fastening system of the cylinder head to the engine block. Its function is to ensure the hermetic connection between the cylinder head and the cylinder, guaranteeing the correct compression of the combustion chamber and preventing gas and coolant leaks. Correct tightening of these screws is essential to maintain the structural integrity of the engine, prevent localized overheating and ensure adequate power transmission to the propeller.

When to replace this part?

Cylinder head bolts can become loose or damaged due to repeated thermal cycling and engine vibration, especially in heavy duty service or after repairs where the cylinder head has been removed. It is recommended to inspect the tightness of these screws at each seasonal inspection and replace any part that shows deformation, corrosion or loss of threads, as well as after any intervention on the cylinder head. Always using genuine Yamaha parts ensures exact geometric compatibility and proper strength, preventing costly leaks and premature engine failure.

Equivalent manufacturer part numbers