Big 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 cylinder NK600.76 with 66 mm bore. Delivery as pictured. Combustion chamber: 66mm. Inlet valves: 25mm. Outlet: 23mm