*Does not fit 2022+ models

Our Koso 4V Head Kit is the ideal engine part to complete the Koso Honda Grom® Big Bore kit. Because of its unique 4 valve design, the air flow and performance are increased. This new designed head is the perfect addition for those who desire more power and torque. The 4 Valve Head Kit features a forged piston, stainless steel 24 mm intake valves and 20 mm exhaust valves. Only fits Koso 170cc big bore kit.

WARNING

THIS IS AN AFTERMARKET PART BUILT FOR RACING PURPOSES ONLY. KOSO IS NOT RESPONSIBLE FOR ANY DAMAGES CAUSED TO THE PARTS, VEHICLE, OR TO YOURSELF AND OTHERS.  ENGINE PARTS ARE NOT UNDER WARRANTY NOR IS COLLATERAL DAMAGE OR COST OF LABOR, IN CASES OF MALFUNCTION.

Specifications

• Cylinder height: 64.2 mm
• Gasket thickness: Upper: 0.25 mm | Bottom: 0.5 mm
• Piston compression: height: 19.5 mm
• Volume: 169.21cc
• Squish: 1mm
• Cylinder head titration: 13.4 cc
• Compression ratio: 12.3 : 1
• Valve / Tappet clearance: IN: 0.10 mm EX: 0.17 mm
• Camshaft: Torque: 1.71 Hp: 26.26 *measured without air filter & no noise reduction plug
• **Requires the use of Iradium spark plug: NGK‑ER9EHIX (part NGK-ER9EH) or Denso # IY27, IY29 or IY31
• Fits for Honda Grom® & HondaMonkey® up to 2021

Instructions