Internal combustion engine of saddle riding vehicle

An internal combustion engine of a saddle riding vehicle, including a crankcase rotatably supporting a crankshaft therein, a cylinder portion fixedly mounted on the crankcase with a cylinder axis inclined relative to a vertical direction, cam shafts of a valve train, a cam chain for transmitting power from the crankshaft to the camshafts, and a cam chain tensioner device for pressing and tensioning the cam chain, wherein:

• the cam chain tensioner device includes a cam chain tensioner swingably supported by the crankcase to contact the cam chain, and a tensioner lifter including a plunger pressing the cam chain tensioner to cause the cam chain tensioner to press and tension the cam chain;
• the tensioner lifter is disposed on an inclined upper surface of the cylinder portion and directed toward the cam chain;
• the engine includes an oil pump, a valve gear oil supply passage for supplying oil from the oil pump to the camshafts, and a tensioner lifter oil supply passage for supplying oil to the tensioner lifter;
• the valve gear oil supply passage has a branching portion where the tensioner lifter oil supply passage branches;
• and
• the branching portion branches at a position higher than the tensioner lifter and communicates with the tensioner lifter disposed at a position lower than the branching portion to send oil into the tensioner lifter.