The Mod Shop in house made 900cc big bore kit is designed for the 650cc or 800cc models. Big bore is 12.5:1 compression, made for 91 octane pump gas. Kit comes with pistons, rings, wrist pin, clips, resleeved cylinder, head and base gaskets. ARP head studs recommended when running the 900cc big bore. We need your cylinders for core. Core charge $300. Fuel tuning required.