Variable valve timing system

A variable valve timing system for an engine in which a cylinder head fixed on a cylinder is suspended on a vehicle body frame and in which a cam chain chamber is formed in the cylinder and the cylinder head, the variable valve timing system comprising:

• a variable valve device configured to change an opening and closing timing of a valve by a hydraulic pressure;
• an oil control valve configured to control the hydraulic pressure with respect to the variable valve device;
• and
• an oil pipe detachably disposed across the cam chain chamber, wherein
• the oil control valve is disposed on an outer surface of the cylinder, which is an outer wall of the cam chain chamber, and the variable valve device is disposed inside the cylinder head, and
• an oil path for hydraulic pressure control enters the outer wall of the cam chain chamber from the oil control valve, and after extending toward a side of the cylinder head from a side of the cylinder, the oil path extends toward the variable valve device through an inner wall of the cam chain chamber through the oil pipe, and
• wherein the oil pipe is a separate component from the cylinder head.