ENGINE (Big Bore Kits, Camshafts and Engine Parts )

Honda Monkey Big Bore Kits

Unlock more power from your Honda Monkey 125 (MSX125) with a big bore kit from Hard Racing. We carry the leading brands in Honda Monkey performance — Takegawa, Kitaco, and Koso — offering displacement upgrades from the stock 125cc to 143cc, 150cc, or 181cc.

Popular Honda Monkey Big Bore Options

The stock Honda Monkey 125 displaces 125cc. A bolt-on big bore kit replaces the cylinder, piston, and rings to increase displacement for more torque and pulling power. Most kits include a new forged piston and cylinder, and some come with high-compression heads or camshafts to fully extract the benefit of the larger bore.

Brands We Carry

Takegawa is Japan's premier source for Monkey 125 bore-up kits, offering 143cc and 181cc options engineered specifically for the MSX125 engine. Kitaco offers reliable 150cc and 181cc forged piston kits for street and sport riding. Koso makes the popular 150cc 4-valve big bore kit designed to pair with their performance camshafts.

Camshafts & Engine Parts

Complement your Honda Monkey big bore kit with a performance camshaft to unlock the full airflow potential of the larger bore. We also carry cylinder head gaskets, cam chains, and all the engine parts needed for a complete Monkey 125 engine build.

Questions? Call 704-799-2192. All orders ship fast from our Charlotte, NC warehouse.