Cylinder Head Nk600.77Cylinder Head 22 25, 66mm for Yamaha X Max, YZF, WR 125Big bore and still not enough? Then we have the Naraku Racing 4 valve cylinder head 66 mm combustion chamber Increased intake, reinforced valve springs and larger valves (23 25 mm). Fits Yamaha X MAX, WR, YZF R 125 and other 125cc mopeds with the YI 3 engine The jets or the injection system must be adjusted (such as with Malossi force master). The cylinder head is suitable for the Naraku big bore