# TBparts - 149cc Big Bore kit with Forged Piston for Grom and Monkey > This is a plain-text (markdown) copy of a page on tboltusa.com, made for AI assistants. People see the same page at the HTML link below. - **Breadcrumbs:** [Home](https://tboltusa.com/store/index.md) > [Japanese Mini Bike Parts](https://tboltusa.com/store/japanese-mini-bike-parts-c-100.md) > [Super Cub C125 - Trail 125 - DAX125](https://tboltusa.com/store/japanese-mini-bike-parts-super-cub-c125-trail-125-dax125-c-100_1148.md) > TBparts - 149cc Big Bore kit with Forged Piston for Grom and Monkey - **Web page:** [this page on tboltusa.com](https://tboltusa.com/store/tbparts-149cc-big-bore-kit-with-forged-piston-for-grom-and-monkey-p-12161.html) - **Markdown:** [this page as markdown](https://tboltusa.com/store/tbparts-149cc-big-bore-kit-with-forged-piston-for-grom-and-monkey-p-12161.md) - **Generated:** 2026-11-03 17:36 EST - **Site guide for AI assistants:** [llms.txt](https://tboltusa.com/llms.txt) - **Your list:** To list everything you have looked at in one page, with current prices and stock, add ids to this address (comma separated, up to 20 of each): `https://tboltusa.com/store/seen.md?p=12161` All prices are in US dollars (USD). Shipping and any tax are worked out at checkout. ## Summary - **Part number:** TBW9263 - **Price:** $239.00 USD - **Stock:** 1 left. This is a kit: the count is how many complete kits can be built from the parts on hand. - **Product id:** 12161 - **Product last changed:** 2023-12-05 ## What it fits The store lists a part under each bike or engine model it is meant for (the categories below) and may name models in the description. Do not assume it fits a bike or engine that is not named here; ask the store first. - [Japanese Mini Bike Parts > Super Cub C125 - Trail 125 - DAX125](https://tboltusa.com/store/japanese-mini-bike-parts-super-cub-c125-trail-125-dax125-c-100_1148.md) - [TB Parts > MSX125 Grom](https://tboltusa.com/store/tb-parts-msx125-grom-c-68_946.md) - [TB Parts > Monkey 2019-present](https://tboltusa.com/store/tb-parts-monkey-2019-present-c-68_1095.md) - [TB Parts > Super Cub C125 - Trail 125 - DAX125](https://tboltusa.com/store/tb-parts-super-cub-c125-trail-125-dax125-c-68_1149.md) Where a fitment line says "All", it means all years of the model named on that line, not all bikes. ## Description (the store's own text) 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. 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. The parts are installed in the same manner as the OEM parts. **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 - 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 **Application:** - Grom - 2022-Present - Monkey - 2022-Present **Kit Includes:** - TBW1596 - 55mm head gasket kit - TBW1585 - 55mm cylinder - TBW1595 - 55mm piston kit **Note:** 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) 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. ## More notes the store shows with this product **Note: **HONDA MONKEY GROM CRF125 and CRF110 2019 - Present fuel injected models ECU will require a flash/tune to prevent a lean condition and possible damage to your engine. CJR cameronjonesracing.com provides this service and can also adjust the tune based on your other modifications.**** ## Shipping and returns - Flat rate shipping is $8 for parts orders under $75 and free for most parts orders over $75, within the continental 48 states. Heavy items (engines, complete bikes, suspension) are excluded. - Full shipping policy: [Shipping policies](https://tboltusa.com/store/shipping-policies-i-6.md) - Returns: the store's own policy page says how returns, exchanges and cancellations work. Please read it before buying: [Returns, Exchanges and Cancellations](https://tboltusa.com/store/returns-exchanges-and-cancellations-i-11.md) The page begins: "All products returned to T Bolt USA must be reviewed and approved." ## How to buy For a person: open [TBparts - 149cc Big Bore kit with Forged Piston for Grom and Monkey](https://tboltusa.com/store/tbparts-149cc-big-bore-kit-with-forged-piston-for-grom-and-monkey-p-12161.html), choose any options, press "Add to Cart", then check out from the cart. Payment is only ever entered by the person, on tboltusa.com's own checkout pages. For an AI assistant building a cart: `https://tboltusa.com/cart/new/item/12161/qty/1` starts one with this product (the first value of every option, qty 1), `https://tboltusa.com/cart//add/item/12161/qty/1` adds it to a cart you already started, and `https://tboltusa.com/cart//zip/` gives the shipping options to a US ZIP code. They answer JSON: give your customer the newest `cart_link`, a public cart link, safe to share. Or give the person one link that fills their own cart when they open it (a public cart link, safe to share; the first value of every option, qty 1): [Put TBparts - 149cc Big Bore kit with Forged Piston for Grom and Monkey in my cart](https://tboltusa.com/cart/open/item/12161/qty/1) Payment: all major credit cards, PayPal, Apple Pay and Google Pay. Money orders by arrangement. Cart: [Shopping cart](https://tboltusa.com/store/shopping_cart.php) ## Photos - [Photo 1](https://tboltusa.com/store/img/p/12161/tbparts-149cc-big-bore-kit-with-forged-piston-for-grom-and-monkey-1.png) ## Support Since 2004, every purchase from TBolt USA includes access to technical support from our staff of experts and our online [Pit Bike Technical Info Database](https://tboltusa.com/store/tbolt-usa-pit-bike-minimoto-technical-info-database-tech-15.md)! We have all necessary support parts on hand. *Most* orders ship same, or next business day, unless otherwise noted above.