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
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