VHM head insert Yamaha YZ 250 99-27 / YZ 250 X 16-27 / Fantic XX 250 21-27 – L 21.00 cc

Exchangeable combustion chamber (insert) for the VHM cylinder head AA33080. Chamber volume 21.00 cc. 🔴 The insert fits ONLY the VHM head AA33080 — it cannot be fitted into the OEM head. For the stock (OEM) piston. Compared with the VHM standard (20.60 cc) it has a larger volume, i.e. lower compression: better over-rev and more top speed at the cost of bottom-end response. It also tolerates lower-octane fuel. Quick to change — the insert simply sits in the head and seals with O-rings. The last characters of the part number are engraved on the insert, so you cannot mix them up. Fits: Yamaha YZ 250 (1999–2027); Yamaha YZ 250 X (2016–2027); Fantic XX 250 (2021–2027).