Ready to wake up your Grom? The Koso North America 170cc Big Bore Cylinder/Head Kit is the definitive displacement upgrade for Honda Grom riders who want real, measurable power gains without sacrificing reliability. Drop the stock 125cc limitations and step up to a purpose-built 170cc setup engineered for performance from the ground up.
The centerpiece is a unique four-valve cylinder head that dramatically improves airflow over the OEM two-valve design — more air in, more power out. Paired with a forged piston for superior strength and heat resistance, this kit is built to handle the demands of spirited street riding, track days, and everything in between.
Features
- 170cc displacement — significant power and torque increase over stock 125cc
- Four-valve cylinder head design for improved airflow and combustion efficiency
- Forged piston for enhanced durability and heat resistance
- Stainless steel 24mm intake valves
- Stainless steel 20mm exhaust valves
- Direct bolt-on fitment — no case splitting required
- Compatible with OG Grom, SF Grom, and 1st Gen Monkey
Fitment
- Honda Grom (OG / MSX125) — All Years
- Honda Grom (SF) — All Years
- Honda Monkey (1st Gen / 125) — All Years
SKU: MB623003 | Weight: 5 lbs
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