# AHP 4 Speed Transmission Z50 CRF50 XR50 & Pit bikes > 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) > [CRF50 Z50 & XR50](https://tboltusa.com/store/japanese-mini-bike-parts-crf50-z50-xr50-c-100_122.md) > [Big Bore & Engine Kits](https://tboltusa.com/store/crf50-z50-xr50-big-bore-engine-kits-c-100_122_124.md) > AHP 4 Speed Transmission Z50 CRF50 XR50 & Pit bikes - **Web page:** [this page on tboltusa.com](https://tboltusa.com/store/ahp-speed-transmission-z50-crf50-xr50-pit-bikes-p-624.html) - **Markdown:** [this page as markdown](https://tboltusa.com/store/ahp-speed-transmission-z50-crf50-xr50-pit-bikes-p-624.md) - **Generated:** 2026-11-10 12:09 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=624` All prices are in US dollars (USD). Shipping and any tax are worked out at checkout. ## Summary - **Part number:** AHP-0624 - **Price:** $159.00 USD - **Stock:** In stock. - **Reviews:** [2 reviews, average 5 of 5](https://tboltusa.com/store/reviews/ahp-speed-transmission-z50-crf50-xr50-pit-bikes-pr-624.html) - **Product id:** 624 - **Product last changed:** 2026-10-04 ## 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 > CRF50 Z50 & XR50 > Big Bore & Engine Kits](https://tboltusa.com/store/crf50-z50-xr50-big-bore-engine-kits-c-100_122_124.md) - [TB Parts > CRF50 XR50 Z50 88-Up > CRF50 XR50 Engine parts](https://tboltusa.com/store/crf50-xr50-z50-88-up-crf50-xr50-engine-parts-c-68_73_996.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) **Note:** ALL TECH SUPPORT and INSTRUCTION email ahpminis@gmail.com AHP 4 speed 1 down 3 up transmission, hardened gears and shift forks. This transmission kit is made for those wanting to upgrade their stock Honda motors from a 3 speed to a 4 speed. AHP's transmission kit will work with both semi-auto and manual clutches and will fit into a OEM Honda bottom end. Will also fit import motors. Set comes complete with main shaft, counter shaft, shift drum,shift forks, and 15T front sprocket. Primary reduction ratio: 3.722 Gear Ratio: 1 - 3.182 2 - 1.706 3 - 1.238 4 - 0.917 All Support on this part will go thru the manufacturer directly mark@ahpminis.com **Note:** When using with 6V points ignition CT and Z50 engines you may need OEM HONDA Kickstart shaft gear 28211-GEL-A80 and OEM HONDA Kickstart shaft 28251-GEL-A80 ## 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 [AHP 4 Speed Transmission Z50 CRF50 XR50 & Pit bikes](https://tboltusa.com/store/ahp-speed-transmission-z50-crf50-xr50-pit-bikes-p-624.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/624/qty/1` starts one with this product (the first value of every option, qty 1), `https://tboltusa.com/cart//add/item/624/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 AHP 4 Speed Transmission Z50 CRF50 XR50 & Pit bikes in my cart](https://tboltusa.com/cart/open/item/624/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/624/ahp-speed-transmission-z50-crf50-xr50-pit-bikes-1.jpg) ## 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.