SKU: 17856293505

TB 149cc Big Bore Kit, 55mm Forged Piston, & Cam – 2022+ Grom/Monkey12

Sale price$135.00 Regular price$150.00
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Ships within 48 hours · Estimated delivery Aug 15 - Aug 20

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Description

TB 149cc Big Bore Kit, 55mm Forged Piston, & Cam – 2022+ Grom/Monkey12TB 149cc Big Bore Kit, 55mm Forged Piston, & Cam 2022+ Grom Monkey12 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

TB 149cc Big Bore Kit, 55mm Forged Piston, & Cam – 2022+ Grom/Monkey12

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. Now included with our performance cam for the best value possible!

TBparts performance camshaft for 2022+ Honda Grom, Monkey, CT125, Dax, & Cub. Ideal for use with our bore kit. Designed with more lift to open both valves up more to let more air and fuel in. More air and fuel equals more power! The cam ramp is also more aggressive to open the valves quicker to sneak even more power out! Unleash more power with this modified performance cam grind!

Key features:
  • 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
  • Brand new performance camshaft & cam bearings
  • 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.

Notes:

  • 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.
  • Valve Lash Settings – 0.003″ Intake/Exhaust

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.

Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 17856293505

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Reviewed in the United States on May 20, 2026
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Reviewed in the United States on February 6, 2026
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