# Big Bore & Engine Kits

> 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
- **Web page:** [this page on tboltusa.com](https://tboltusa.com/store/crf50-z50-xr50-big-bore-engine-kits-c-100_122_124.html)
- **Markdown:** [this page as markdown](https://tboltusa.com/store/crf50-z50-xr50-big-bore-engine-kits-c-100_122_124.md)
- **Generated:** 2026-11-05 07:19 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?c=124`

All prices are in US dollars (USD). Shipping and any tax are worked out at checkout.

Products are filed in categories. Most top categories split by bike or engine model; a product can be listed in more than one category.

## Next to this category

- [Bars & Controls](https://tboltusa.com/store/crf50-z50-xr50-bars-controls-c-100_122_130.md)
- [Brake Pads & Pedals](https://tboltusa.com/store/crf50-z50-xr50-brake-pads-pedals-c-100_122_199.md)
- [Carb kits](https://tboltusa.com/store/crf50-z50-xr50-carb-kits-c-100_122_125.md)
- [Electrical](https://tboltusa.com/store/crf50-z50-xr50-electrical-c-100_122_128.md)
- [Engine Covers & Dress Up Parts](https://tboltusa.com/store/crf50-z50-xr50-engine-covers-dress-up-parts-c-100_122_506.md)
- [Exhaust Pipes](https://tboltusa.com/store/crf50-z50-xr50-exhaust-pipes-c-100_122_131.md)
- [Frames & Swingarms](https://tboltusa.com/store/crf50-z50-xr50-frames-swingarms-c-100_122_507.md)
- [Front Forks](https://tboltusa.com/store/crf50-z50-xr50-front-forks-c-100_122_129.md)
- [Pegs & Mounts](https://tboltusa.com/store/crf50-z50-xr50-pegs-mounts-c-100_122_139.md)
- [Plastics & Graphics](https://tboltusa.com/store/crf50-z50-xr50-plastics-graphics-c-100_122_505.md)
- [Rear Shocks & Skid plates](https://tboltusa.com/store/crf50-z50-xr50-rear-shocks-skid-plates-c-100_122_508.md)
- [Seats & Tanks](https://tboltusa.com/store/crf50-z50-xr50-seats-tanks-c-100_122_138.md)
- [Sprockets & Chains](https://tboltusa.com/store/crf50-z50-xr50-sprockets-chains-c-100_122_503.md)
- [Wheels and Tires](https://tboltusa.com/store/crf50-z50-xr50-wheels-and-tires-c-100_122_504.md)

## Products

Showing 1 to 24 of 26 products (page 1 of 2).

- [TBParts - 88cc Big Bore Kit for Z50 CRF50 XR50 1988-Present](https://tboltusa.com/store/tbparts-88cc-big-bore-kit-for-z50-crf50-xr50-1988-present-p-759.md): part number `TBW0928`; $149.99 USD; 8 left
- [TBParts - Heavy Duty Clutch Kit for 67T- CRF70 , XR70 , Z50 69-87 ,CT70 K0 and 91-94 Models](https://tboltusa.com/store/tbparts-heavy-duty-clutch-kit-for-67t-crf70-xr70-z50-69-87-ct70-k0-and-91-94-models-p-415.md): part number `TBW0971-KIT`; $99.98 USD; 4 left
- [TBParts - Manual Clutch kit Z50 CRF50/70 XR50/70 & Pit bikes](https://tboltusa.com/store/tbparts-manual-clutch-kit-z50-crf5070-xr5070-pit-bikes-p-273.md): part number `TBW0953`; $189.99 USD; 4 left
- [TBParts - Roller Rocker Race Head V2 108cc Big Bore Kit Z50 CRF50 XR50 & Pit bikes](https://tboltusa.com/store/tbparts-roller-rocker-race-head-v2-108cc-big-bore-kit-z50-crf50-xr50-pit-bikes-p-8607.md): part number `TBW9109`; $729.99 USD; 2 left
- [TBparts - Roller Rocker Race Head V2 88cc Big Bore Kit Z50 CRF50 XR50 & Pit bikes w/ Mikuni VM24 Carb](https://tboltusa.com/store/tbparts-roller-rocker-race-head-v2-88cc-big-bore-kit-z50-crf50-xr50-pit-bikes-mikuni-vm24-carb-p-8727.md): part number `TBW9115`; $774.99 USD; 2 left
- [TBParts - Roller Rocker Race Head V2 Kit for 88cc & 108cc Z50 CRF50 XR50 & Pit bikes](https://tboltusa.com/store/tbparts-roller-rocker-race-head-v2-kit-for-88cc-108cc-z50-crf50-xr50-pit-bikes-p-8600.md): part number `TBW9102`; $549.99 USD; 2 left
- [TBParts 88cc Big Bore Kit, Race Cam and 20mm Carb Kit for Z50 CRF50 XR50 88-Present](https://tboltusa.com/store/tbparts-88cc-big-bore-kit-race-cam-and-20mm-carb-kit-for-z50-crf50-xr50-88-present-p-396.md): part number `TBW0930`; $269.99 USD; out of stock
- [50cc Rebuild kit with Gasket set for Honda CRF50 XR50](https://tboltusa.com/store/50cc-rebuild-kit-with-gasket-set-for-honda-crf50-xr50-p-12657.md): part number `TRC-3074`; $99.00 USD; out of stock
- [AHP 4 Speed Transmission Z50 CRF50 XR50 & Pit bikes](https://tboltusa.com/store/ahp-speed-transmission-z50-crf50-xr50-pit-bikes-p-624.md): part number `AHP-0624`; $159.00 USD; in stock
- [All Balls - Crankshaft Bearing - Honda 50s, 70s, XL/XR75](https://tboltusa.com/store/all-balls-crankshaft-bearing-honda-50s-70s-xlxr75-p-5566.md): part number `W-22-41031`; $39.88 USD; 1 left
- [EBC - Redline Clutch Kit for CRF50/70](https://tboltusa.com/store/ebc-redline-clutch-kit-for-crf5070-p-10367.md): part number `W-15-1148`; $20.50 USD; 2 left
- [Honda - OEM Ball Retainer for CRF50 and XR50](https://tboltusa.com/store/honda-oem-ball-retainer-for-crf50-and-xr50-p-9059.md): part number `22860-GEL-A80`; $7.99 USD; 1 left
- [Honda 50cc Rebuild kit with Full gasket Z50R XR50 CRF50 1988 - Present](https://tboltusa.com/store/honda-50cc-rebuild-kit-with-full-gasket-z50r-xr50-crf50-1988-present-p-12407.md): part number `TRC-2760`; $99.00 USD; 2 left
- [TBParts - Gasket Kit and Oil Seal Kit for Stock bore - Z50 88-99 All XR50 and CRF50](https://tboltusa.com/store/tbparts-gasket-kit-and-oil-seal-kit-for-stock-bore-z50-88-99-all-xr50-and-crf50-p-1270.md): part number `TBW1590`; $34.99 USD; out of stock
- [TBParts - H-D Auto Clutch Kit 69T Z50 CRF50 XR50 ATC70 & Pit bikes](https://tboltusa.com/store/tbparts-auto-clutch-kit-69t-z50-crf50-xr50-atc70-pit-bikes-p-303.md): part number `TBW0961`; $91.99 USD; 6 left
- [TBParts - Magnetic Oil Drain Bolt - XR50 CRF50 CRF70 KLX110 & Pit Bikes](https://tboltusa.com/store/tbparts-magnetic-oil-drain-bolt-xr50-crf50-crf70-klx110-pit-bikes-p-271.md): part number `TBW0341`; $6.99 USD; in stock
- [TBparts - Oil seal and O-ring Kit for CT70, Z50, XR/CRF 50/70 and China 50-160cc](https://tboltusa.com/store/tbparts-oil-seal-and-ring-kit-for-ct70-z50-xrcrf-5070-and-china-50-160cc-p-2130.md): part number `TBW1028-0291`; $15.00 USD; 4 left
- [TBParts - Race Head Kit for 88cc For Z50 CRF50 XR50 & Pit bikes](https://tboltusa.com/store/tbparts-race-head-kit-for-88cc-for-z50-crf50-xr50-pit-bikes-p-45.md): part number `TBW0934`; $264.99 USD; in stock
- [TBParts - Race Head, 88cc Big Bore and 20mm Carb Kit for Z50 CRF50 XR50 CRF70](https://tboltusa.com/store/tbparts-race-head-88cc-big-bore-and-20mm-carb-kit-for-z50-crf50-xr50-crf70-p-883.md): part number `TBW0936`; $419.99 USD; in stock
- [TBparts - Replacment Clutch Kit for Honda 50 and 70 Semi-Auto](https://tboltusa.com/store/tbparts-replacment-clutch-kit-for-honda-50-and-70-semi-auto-p-2796.md): part number `TBW1907`; $24.95 USD; 5 left
- [TBParts - Stock Shift Shaft - Z50 XR50 CRF50 XR70 CRF70 - 1988 - present](https://tboltusa.com/store/tbparts-stock-shift-shaft-z50-xr50-crf50-xr70-crf70-1988-present-p-1780.md): part number `TBW1222`; $24.99 USD; 3 left
- [TBParts - Stroker kit 1 108cc for Z50 CRF50 XR50 CRF70](https://tboltusa.com/store/tbparts-stroker-kit-108cc-for-z50-crf50-xr50-crf70-p-43.md): part number `TBW0966`; $189.99 USD; 4 left
- [TBParts - Stroker kit 2 108cc for Z50 CRF50 XR50 CRF70](https://tboltusa.com/store/tbparts-stroker-kit-108cc-for-z50-crf50-xr50-crf70-p-268.md): part number `TBW0967`; $352.99 USD; 4 left
- [TBParts - Stroker kit 3 108cc with Race Head for Z50 CRF50 XR50 CRF70](https://tboltusa.com/store/tbparts-stroker-kit-108cc-with-race-head-for-z50-crf50-xr50-crf70-p-269.md): part number `TBW0968`; $612.99 USD; 4 left

Stock: "in stock" = 9 or more, a number = that many left, "out of stock" = cannot be ordered now. "options" = choose options on the product page before it can go in the cart. Product links go to the markdown copy; for the web page change the ending .md to .html.

- [Next page (page 2)](https://tboltusa.com/store/crf50-z50-xr50-big-bore-engine-kits-c-100_122_124.md?page=2)

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