GROM

Honda Grom Big Bore Kits

Upgrade your Honda Grom or MSX125 with performance big bore kits from Takegawa, Kitaco, and Koso. Bore-up kits are the most impactful single engine modification for the Grom, increasing displacement from 125cc to 150cc, 170cc, or 181cc.

Grom Big Bore Kit Options

Choose from multiple displacement options for your Honda Grom build. The 150cc kit delivers a significant torque increase while retaining excellent reliability. The 170cc and 181cc options are popular with performance-oriented riders. All kits include a bore-up cylinder, piston, rings, and gaskets.

Brands: Takegawa, Kitaco & Koso

Hard Racing stocks Grom big bore kits from the top Japanese performance brands. Takegawa and Kitaco both offer 181cc kits with camshaft options. Koso offers the popular 170cc kit. All are direct-fit for 2013–2025 Honda Grom and MSX125.