TBParts 186cc Big Bore Kit (64mm) – Honda Grom & Monkey (2014–2021)

NOT LEGAL FOR SALE OR USE IN CALIFORNIA ON ANY POLLUTION CONTROLLED MOTOR VEHICLES. Intended for closed-course competition and off-road use only.

IMPORTANT: This kit fits 2021 and older Grom & Monkey models only. It is NOT compatible with the 2022+ models — the engine was redesigned for that generation.

TBParts 186cc Big Bore Kit (64mm) – Honda Grom & Monkey (2014–2021)

The biggest bore kit available for the Honda Grom and 1st Gen Monkey — and it requires zero case machining. The TBParts 186cc kit pairs a ceramic-coated all-aluminum 64mm cylinder with a lightweight high-compression piston to deliver a dramatic power increase and make your bike a lot more fun to ride.

The ceramic-coated aluminum cylinder is lighter than a steel-sleeved alternative, reduces friction for more power, improves sealing, and transfers heat more efficiently. High quality parts, real results, bolt-on installation.

What’s Included

• Ceramic-coated all-aluminum 64mm cylinder (no steel sleeve)
• Lightweight 64mm piston with rings, pin & clips
• Head gasket kit

Available Options

• Without Oil Cooler — Big bore kit only (TBW9150)
• With Oil Cooler — Big bore kit + oil cooler for thermal management (TBW9154)
• With Oil Cooler & Camshaft — Full performance package with oil cooler and performance cam (TBW9183)

Tuning Requirements

An aftermarket fuel controller is required to prevent a lean condition and potential engine damage. Professional installation is recommended.

Fitment

• Honda Grom OG (2014–2015)
• Honda Grom SF (2017–2020)
• Honda Monkey 1st Gen (2018–2021)
• NOT compatible with 2022+ Grom or Monkey