Kitaco DOHC Twin Cam 181cc Big Bore Kit – Honda Grom & Monkey 125 (2014–2021)

Kitaco DOHC Twin Cam 181cc Big Bore Kit – The Ultimate Grom & Monkey 125 Engine Upgrade

The Kitaco DOHC 181cc Big Bore Kit is the pinnacle of performance engine upgrades for the Honda Grom and Monkey 125. Featuring a full Dual Overhead Cam (DOHC) cylinder head, forged internals, and a hard-plated 181cc cylinder, this kit delivers aggressive power output and torque that no SOHC big bore kit can match. If you want to stand out and make serious power, this is the build.

What’s Included

• Dual Overhead Cam (DOHC) Cylinder Head — optimized combustion chamber shape with high-efficiency port design
• Dual Camshafts — high-lift profiles for aggressive intake and exhaust timing
• 181cc Forged Piston — high-compression forged construction for increased displacement and durability
• 181cc Hard-Plated Aluminum Cylinder — precision-bored for longevity under race conditions
• Piston rings, pin, clips & gasket kit — complete sealing hardware included
• Kitaco Forged H-Beam Crankshaft & H-Style Connecting Rod — handles sustained high-RPM demands
• Reinforced Cam Chain — upgraded for reliability at elevated engine speeds
• Heavy-Duty Valve Springs — prevents float at high RPM
• Heavy-Duty Cylinder Studs — secure head clamping under increased cylinder pressure
• Hi-Flow Fuel Injector — supports increased fuel demand of the 181cc displacement

Engine Specifications

• Displacement: 181cc
• Bore: φ63mm
• Stroke: 57.9mm (stock)
• Compression Ratio: 11.5:1
• Intake Valves: 24.5mm
• Exhaust Valves: 21mm
• Intake Port: 28mm
• Exhaust Port: 23mm
• Fuel Requirement: Premium octane gasoline required
• Decompressor: No decomp function built-in

Fitment

• Honda Grom (MSX125) — 2014–2020, 4-speed only
• Honda Monkey 125 — 2018–2021, 4-speed only
• Does NOT fit 2022+ Grom or 2022+ Monkey 125 (5-speed)

Important Installation Notes

• Professional installation is strongly recommended
• Engine break-in procedure is required after installation
• An aftermarket fuel controller and custom tune/autotune are required — fuel controller is NOT included
• This kit converts your engine to a high-performance race configuration requiring additional maintenance attention

Warranty Disclaimer

No warranty is stated or implied on race engine parts or bore-up kits due to the unusual stresses placed on these components and because we have no control over installation or use. Installation and use of this product constitutes full assumption of responsibility by the user.

Part Number: 215-1432900