After being a protagonist for 30 years, the everlasting Ø 61 cast-iron cylinder kit, art. 31 4093, updates! Constantly refined over the years, the legendary Ø 61 has now a new code, after undergoing further upgrade concerning above all the main and rear transfer ports. It is the one and only cylinder kit of its kind using an o-ring as sealing gasket between head and cylinder, in order to guarantee better sealing and heat dissipation. By improving torque at low RPMs, this cylinder kit further increases performance. With this development Malossi technicians went beyond all expectations once again! TECHNICAL FEATURES Cylinder Material: special self-lubricating, wear-resistant, highly refined cast iron alloys, obtained by Shell Moulding gravity die-casting. Machining: on numerically controlled high precision machine tools. Recalculated and increased heat exchange surfaces. Exhaust and transfer ports designed and tuned for maximum thermodynamic performance. Dimensional and surface finish quality control performed according to Malossi's internal specifications. Cylinder and piston selected for a 100% fit of 0.010-0.005 mm. Checking of all the seals carried out. Piston Material: special aluminium alloy with high silicon content and low thermal expansion. Machining: on numerically controlled machine tools. Lightened and strengthened. Heat exchange surfaces increased. Piston rings Piston rings in very strong modular cast iron with ground, wear-resistant, hard chrome metal-spray coating on the contact surface. Head Material: special die-cast aluminium alloy. Geometry of heat exchange surfaces recalculated and increased. Machining: numerically controlled high precision machines with diamond tools. Surface rust prevention treatment. Viton Head Gasket. Hemispheric combustion chamber with centred squish and spark plug.