TB 149cc Big Bore Kit, 55mm Forged Piston – 2022+ Grom/Monkey125
TBparts 149cc big bore kit for the 2022+ Honda Grom/Monkey 125. This will make your motorcycle a lot more fun to ride by adding some much needed power. With the larger bore, this bolt-on upgrade kit will give you more power and higher compression for a very reasonable price. This kit does not require boring of the case – simply bolt on, tune (Not included) and go!! This is an ideal option if you’re looking to add some power or you just need a new cylinder, piston, and rings to rebuild your engine.
- High quality, Forged, high compression 55mm piston, with rings, pin, & clips
- 11.8:1 compression ratio compared to Stock 10:1. Our 11.8:1 piston is pump 91+ octane gas friendly.
- Aluminum cylinder with steel sleeve (55mm)
- Head gasket kit with exhaust gasket!
- Fits all 2022+ Honda Grom/Monkey 125
- Largest bore you can go without boring the cases
- More power and fun at an affordable price
- Clearance to retain factory piston oil squirter
- Easy bolt-on kit
- +4 HP! More gains if you have a performance Exhaust and Intake
There are no installation instructions, but if you can replace your piston, you can install this kit. If you don’t have any experience working on your engine, we highly recommend having a professional technician install this kit or, at a minimum, purchasing the shop manual for your bike. We also have a link on our website in the INFO section under Honda where you can find additional info. The parts are installed in the same manner as the OEM parts.
- These bore kits are only for the 2022 and newer models (will not work on the 2021 and older models as the engine has been redesigned)
- A performance intake and exhaust is recommended if you want to get the most power possible! (Not necessary)
- Tuning Required – The ECU will require a flash/tune to prevent a lean condition and possible damage to your engine. CJR Performance (cameronjonesracing.com) provides this service and can also adjust the tune based on your other modifications.
This product is legal for closed-course competition use only; for racing vehicles (a competition vehicle not used on public highways). Intended for off-road use or race purposes; may not meet regulations of pollution controlled roads or highways. Not legal for vehicles registered and use in California.