{"title":"Pit Bike Big Bore Kits","description":"\u003cdiv class=\"category-top-desc\"\u003e\n\u003cp\u003eStage 1, Stage 2 \u0026amp; stroker big bore kits for Honda CRF50, XR50, CRF70, XR70, Z50, CT70 \u0026amp; more\u003c\/p\u003e\n\u003cp\u003eBump displacement from stock to 88cc, 108cc or 117cc — modern and vintage Honda 50\/70 platforms\u003c\/p\u003e\n\u003c\/div\u003e","products":[{"product_id":"performance-camshaft-for-honda-crf50","title":"Performance Camshaft for Honda CRF50","description":"\n\u003cp\u003e\u003cstrong\u003e50 Caliber Racing High Performance Race Camshaft for Honda CRF50 Pit Bikes\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003ePerformance camshaft with much more aggressive lift and duration. Increase power with a simple camshaft change. For STOCK or RACE head 92-up Honda pit bikes. Goes well with 88cc big bore kits and aftermarket CDI.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eSpecs:\u003c\/strong\u003e\u003cbr\u003e- .235″ intake valve lift and 196 degrees of duration @ 050″, .218″ exhaust valve lift and 208 degrees of duration @ .050″\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits the following Honda pit bikes: \u003c\/strong\u003e\u003cbr\u003e- CRF50 (2004-2018)\u003cbr\u003e- CRF70 (2004-2018)\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236485177601,"sku":"4448A12","price":55.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/6906.jpg?v=1780777660"},{"product_id":"88cc-stage-2-vintage-big-bore-kit-for-honda-z50-ct70-atc70-trx70-sl70-xl70","title":"88cc Stage 2 Vintage Big Bore Kit for Honda Z50, CT70, ATC70, TRX70, SL70, XL70","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing Vintage Stage 2 88cc Big Bore kit for Honda Z50 CT70 SL70 XL70 ATC70 \u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e Vintage stage 2 88cc big bore kit has an improved lightweight 52mm piston and cylinder design, with oversized cooling fins for efficient heat dissipation. Includes a 20mm performance carb assembly, and all the gaskets needed for install. Can be installed by anyone with basic mechanical skills who is not afraid to turn some nuts and bolts. Breathe new life into your Honda with our high quality, affordable, and reliable big bore kit!\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIncludes:\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e - Lightweight aluminum cylinder with steel sleeve\u003cbr\u003e - Cast in mounts on cylinder for aftermarket skid plates\u003cbr\u003e - Oversized cooling fins on cylinder for efficient heat dissipation\u003cbr\u003e - High compression 52mm piston with rings, pin, \u0026amp; clips (you can still run pump gas)\u003cbr\u003e - Head gasket kit\u003cbr\u003e - 20mm Performance carburetor kit with intake, heat-stop, gaskets, and hardware \u003cbr\u003e- Performance air filter\u003cbr\u003e- Long throttle cable (twist throttle style)\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits the following Honda bikes:\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e - Z50 (1968-1978) K0-78\u003cbr\u003e - CT70 (1968-1981) K0-81\u003cbr\u003e - ATC70 (1973-1985)\u003cbr\u003e - TRX70 (1986-1987)\u003cbr\u003e - SL70 (1971-1973)\u003cbr\u003e - XL70 (1974-1976)\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236486095105,"sku":"4447A2","price":240.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8797.jpg?v=1780777859"},{"product_id":"88cc-vintage-big-bore-kit-with-race-head-honda-z50-ct70-atc70-68-81","title":"88cc Vintage Big Bore Kit with Race Head Honda Z50, CT70, ATC70 68-81","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing 88cc Vintage Big Bore Kit with Race Head for Honda Z50, CT70, ATC70, SL70 \u0026amp; XL70 Pit Bikes 1968-1981\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e 88cc Race head kit for Your Honda pit bike. This kit will drastically improve your overall performance on your bike. A stock Honda 50 puts around 2.2 hp to the ground and this kit will put you between 5.5-6 hp to the ground and 30% more to the crank! Kit comes with fully assembled race head, performance cam, 20mm carburetor, and all the other goodies needed to fulfill your need for speed!\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIncludes:\u003c\/strong\u003e\u003cbr\u003e - Lightweight aluminum cylinder with steel sleeve\u003cbr\u003e - Cast in mounts on cylinder for aftermarket skid plates\u003cbr\u003e - Oversized cooling fins on cylinder for efficient heat dissipation\u003cbr\u003e - High compression 52mm piston with rings, pin, \u0026amp; clips (you can still run pump gas)\u003cbr\u003e - Fully assembled race head with 25\/22mm valves for increased air flow\u003cbr\u003e - High performance race camshaft and cam sprocket\u003cbr\u003e - 20mm Performance carburetor kit with intake, heatstop, gaskets, and hardware\u003cbr\u003e - Performance foam air filter\u003cbr\u003e - Long throttle cable (twist throttle style)\u003cbr\u003e- Gasket kit \u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits the following Honda Pit Bikes:\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e - Z50A (1968-1978) K0-78\u003cbr\u003e - CT70 (1969-1982) K0-81\u003cbr\u003e - ATC70 (1973-1985)\u003cbr\u003e - SL70 (1971-1973)\u003cbr\u003e - XL70 (1974-1976)\u003cbr\u003e\u003cbr\u003e We have been selling these kits since 2004 and believe they are of the highest quality and put out the most power you are going to find in a Big Bore kit period.\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236486193409,"sku":"4448A1","price":409.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8805.jpg?v=1780777889"},{"product_id":"honda-z50-stage-1-big-bore-kit-vintage-ct70-atc70-trx70-sl70-xl70","title":"Honda Z50 Stage 1 Big Bore Kit Vintage CT70 ATC70 TRX70 SL70 XL70","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing Honda Z50 Stage 1 Vintage Big Bore kit - Z50 CT70 SL70 XL70 ATC70 TRX70\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e Vintage Stage 1 88cc big bore kit has an improved lightweight 52mm piston and cylinder design, with oversized cooling fins for efficient heat dissipation. Includes all gaskets needed for install. Can be installed by anyone with basic mechanical skills who is not afraid to turn some nuts and bolts. Breathe new life into your Honda with our high quality, affordable, and reliable big bore kit!\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIncludes:\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e - Lightweight aluminum cylinder with steel sleeve\u003cbr\u003e - Cast in mounts on cylinder for aftermarket skid plates\u003cbr\u003e - Oversized cooling fins on cylinder for efficient heat dissipation\u003cbr\u003e - High compression 52mm piston with rings, pin, \u0026amp; clips (you can still run pump gas)\u003cbr\u003e - Head gasket kit\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits the following Honda bikes:\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e - Z50 (1968-1978) K0-78\u003cbr\u003e - CT70 (1968-1981) K0-81\u003cbr\u003e - ATC70 (1973-1985)\u003cbr\u003e - TRX70 (1986-1987)\u003cbr\u003e - SL70 (1971-1973)\u003cbr\u003e - XL70 (1974-1976)\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236486226177,"sku":"4446A2","price":155.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8795.jpg?v=1780777925"},{"product_id":"honda-70-stage-1-big-bore-kit-xr70-crf70","title":"Honda 70 Stage 1 Big Bore Kit XR70 CRF70","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing Stage 1 88cc Big Bore kit (52mm bore) for Honda XR70 and CRF70\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003cspan\u003eOur 50 Caliber Racing Stage 1 Big Bore Kits are top quality and come with everything you need to finish the job. This is a great way to pump up your Honda XR70 or CRF70. This kit is recommended for those who don't want to spend a fortune but still want to see a nice power increase over the stock engine. It can be installed by anyone with basic mechanical skills who isn't afraid to turn some nuts and bolts.\u003c\/span\u003e\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIncludes:\u003c\/strong\u003e\u003cbr\u003e\u003cspan\u003e- Lightweight aluminum cylinder with steel sleeve\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003e- Cast in mounts on cylinder for aftermarket skid plates\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003e- Oversized cooling fins on cylinder for efficient heat dissipation\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003e- High compression 52mm piston with rings, pin, \u0026amp; clips (can still run pump gas)\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003e- Head gasket kit includes all gasket needed to install big bore kit\u003c\/span\u003e\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits:\u003c\/strong\u003e\u003cbr\u003e\u003cspan\u003eHONDA\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003e-  XR70 (1997-2003)\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003e- CRF70 (2004-2016)\u003c\/span\u003e\u003cbr\u003e\u003cbr\u003e\u003cspan\u003e*High volume oil pump is recommended\u003c\/span\u003e\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236486717697,"sku":"4446A1","price":155.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8815.jpg?v=1780778006"},{"product_id":"honda-70-stage-2-big-bore-kit-xr70-crf70","title":"Honda 70 Stage 2 Big Bore Kit XR70 CRF70","description":"\n\u003cp\u003e\u003cstrong\u003e50 Caliber Racing Stage 2 88cc Big Bore Kit for Honda XR70 and CRF70 (All Years)\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003eOur 50 Caliber Racing Big Bore Kits are top quality and come with everything you need to finish the job. This is a great way to pump up your Honda 70. This kit will easily double the stock horse power on your bike. We recommend installing a high volume oil pump with this kit.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIncludes:\u003c\/strong\u003e\u003cbr\u003e- Lightweight aluminum cylinder with steel sleeve\u003cbr\u003e- Cast in mounts on cylinder for aftermarket skid plates\u003cbr\u003e- Oversized cooling fins on cylinder for efficient heat dissipation\u003cbr\u003e- High compression 52mm piston with rings, pin, \u0026amp; clips (you can still run pump gas)\u003cbr\u003e- Head gasket kit, all gasket included needed for install.\u003cbr\u003e- High performance race camshaft\u003cbr\u003e- 20mm Performance carb assembly. Includes: 20mm carb, intake, heat-stop, gaskets, mounting\u003cbr\u003ehardware\/wrench and air filter\u003cbr\u003e- Extended throttle cable (to fit aftermarket hand throttle)\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits:\u003c\/strong\u003e\u003cbr\u003eHONDA\u003cbr\u003e- XR70 (All years)\u003cbr\u003e- CRF70 (All years)\u003cbr\u003e\u003cbr\u003e*High volume oil pump is recommended\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236486816001,"sku":"4447A1","price":279.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8826.jpg?v=1780778041"},{"product_id":"88-up-honda-50-stage-1-big-bore-kit-z50-xr50-crf50","title":"88-Up Honda 50 Stage 1 Big Bore Kit - Z50 XR50 CRF50","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing Stage 1 88cc Big Bore kit (52mm bore) for Z50 (1988-1999), XR and XR50 \/ CRF 50 (2000-Present)\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e Our 50 Caliber Racing Stage 1 Big Bore Kit is top quality and come with everything you need to finish the job. This is a great way to pump up your Honda Z50, XR50 or CRF50. This kit is recommended for those who don't want to spend a fortune but still want to see a nice power increase over the stock engine. It can be installed by anyone with basic mechanical skills who isn't afraid to turn some nuts and bolts.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIncludes:\u003c\/strong\u003e\u003cbr\u003e - Lightweight aluminum cylinder with steel sleeve\u003cbr\u003e - Cast in mounts on cylinder for aftermarket skid plates\u003cbr\u003e - Oversized cooling fins on cylinder for efficient heat dissipation\u003cbr\u003e - High compression 52mm piston with rings, pin, \u0026amp; clips (can still run pump gas)\u003cbr\u003e - Head gasket kit includes all gasket needed to install big bore kit\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits:\u003c\/strong\u003e\u003cbr\u003e HONDA\u003cbr\u003e - Z50 (1988-1999)\u003cbr\u003e - XR50 (2000-Present)\u003cbr\u003e - CRF50 (2000-Present)\u003cbr\u003e\u003cbr\u003e *High volume oil pump is recommended\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236486848769,"sku":"4446","price":155.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8688.jpg?v=1780778076"},{"product_id":"88cc-big-bore-kit-with-race-head-honda-z50-crf50-xr70-crf70","title":"88cc Big Bore Kit with Race Head - Honda Z50, CRF50, XR70 \u0026 CRF70","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing 88cc Big Bore Kit with Race Head for Honda CRF50, XR50, CRF70 \u0026amp; XR70 Pit Bikes\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e 88cc Race head kit for your Honda 50 or Honda 70. This kit will drastically improve your overall performance on your bike. A stock Honda 50 puts around 2.2 hp to the ground and this kit will put you between 5.5-6 hp to the ground and 30% more to the crank! Kit comes with fully assembled race head, performance cam, 20mm carburetor, and all the other goodies needed to fulfill your need for speed!\u003cbr\u003e\u003cbr\u003e \u003cstrong\u003eSpecifications:\u003c\/strong\u003e\u003cbr\u003e - Comes with fully assembled race head (with larger valves for significantly increased air flow)\u003cbr\u003e - Performance CDI box included that removes stock rev limiter\u003cbr\u003e - Lightweight aluminum cylinder with steel sleeve\u003cbr\u003e - Cast in mounts on cylinder for aftermarket skid plates\u003cbr\u003e - Oversized cooling fins on cylinder for efficient heat dissipation\u003cbr\u003e - 52mm piston with rings, pin, \u0026amp; clips\u003cbr\u003e - Head gasket kit\u003cbr\u003e - High performance race camshaft\u003cbr\u003e - 20mm Performance carb assembly. Includes: 20mm carb, intake, heatstop, gaskets, mounting \u003cbr\u003ehardware\/wrench and air filter\u003cbr\u003e - Extended throttle cable (to fit aftermarket hand throttle)\u003c\/p\u003e\n\u003cp\u003e* High volume oil pump recommended, but not included\u003cbr\u003e\u003cbr\u003e \u003cstrong\u003eFits the following Honda pit bikes:\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e - CRF50F (2004-2022)\u003cbr\u003e - CRF70F (2004-2012)\u003cbr\u003e - XR50R (2000-2004)\u003cbr\u003e - XR70R (1997-2004)\u003cbr\u003e - Z50R (1988-1999)\u003cbr\u003e\u003cbr\u003e We have been selling these kits since 2004 and believe they are of the highest quality and put out the most power you are going to find in a Big Bore kit period.\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236487078145,"sku":"4448","price":399.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8699.jpg?v=1780778112"},{"product_id":"108cc-stroker-kit-2-for-honda-50-70-pit-bikes","title":"108cc Stroker Kit 2 for Honda 50 70 Pit Bikes","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing 108cc Stroker Kit #2 for Honda CRF50, XR50, CRF70, XR70 pit bikes\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e This is hands down the biggest and baddest big bore kit we offer for your Honda 50cc and 70cc pit bike. Complete with 51mm stroker crank and 52mm piston \u0026amp; cylinder, this kit will increase total displacement to 108cc. This kit includes everything in our Stage 2 Race Head kit, plus a 51mm stroker crank which will add up to additional 2 horsepower over a standard 88cc race head kit. All the components are made specifically for 1988 and newer engines so there will be no fitment issues and boring of the case will not be necessary. A genuine Honda engine upgraded with this kit will stomp any of the Chinese Honda clones up to 125cc. We have been selling these kits since 2004 and have had nothing but great results and happy customers!\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eKit includes:\u003c\/strong\u003e\u003cbr\u003e - 51mm Crankshaft\u003cbr\u003e - High compression piston with rings, pin, \u0026amp; clips (Runs on pump gas 91 octane)\u003cbr\u003e - Fully assembled Race Head: Larger valves and porting for increased performance. Also has bigger cooling fins\u003cbr\u003e - Lightweight aluminum cylinder with steel sleeve, cast in mounts for skid plates, and larger cooling fins\u003cbr\u003e - High performance race camshaft\u003cbr\u003e - 24mm Carburetor kit with intake, air filter, and throttle cable\u003cbr\u003e - Crankcase and clutch cover gaskets\u003cbr\u003e - Head gasket kit\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eWe recommend the following items be installed along with this kit. They are not included:\u003c\/strong\u003e\u003cbr\u003e - High volume oil pump\u003cbr\u003e - Oil Cooler\u003cbr\u003e - Performance Cdi Rev box\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits the following Honda Pit Bikes:\u003c\/strong\u003e\u003cbr\u003e - XR50 (1988-up)\u003cbr\u003e - CRF50 (1988-up)\u003cbr\u003e - XR70 (1988-up)\u003cbr\u003e - CRF70 (1988-up)\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003ePlease note:\u003c\/strong\u003e\u003cbr\u003e -Installation requires the engine case to be split. You will need a Honda manual and proper tools to complete install. We highly recommend having a professional shop install this kit as it does not come with installation instructions and is very technical.\u003cbr\u003e\u003cbr\u003e - This is a complete stock to 108cc conversion kit and includes a 52mm race head big bore kit. If you have already upgraded we offer a conversion Stroker Kit #1 that includes only the necessary parts to convert an 88cc race head engine to a 108cc stroker engine, search our eBay store for part # 4448-A2.\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236487209217,"sku":"4448A3","price":525.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/3380.jpg?v=1780778152"},{"product_id":"117cc-stroker-kit-6-with-race-head-for-honda-crf50-xr50-crf70","title":"117cc Stroker Kit 6 with Race head for Honda CRF50, XR50 \u0026 CRF70","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing 117cc Stroker Kit #6 with Race Head for Honda CRF50, XR50, CRF70, XR70 Pit Bikes\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e Contains everything you need to convert your completely stock engine into a powerful open class 117cc engine (much more powerful than the common Chinese 107 and 125cc engines) with tons of torque! Also, this crank was made specifically for the newer engines and thus, you will not have any fitment issues like trimming the piston skirts in order to clear the crank or the piston not lining up with the cylinder deck.\u003cbr\u003e\u003cbr\u003e \u003cstrong\u003eKit includes:\u003c\/strong\u003e\u003cbr\u003e - 51mm Crankshaft with NTN Bearings\u003cbr\u003e- Fully assemble Race Head with larger valves for significantly increased airflow\u003cbr\u003e- High performance race camshaft\u003cbr\u003e - Lightweight 54mm aluminum cylinder with steel sleeve, cast in mounts for skid plates, and larger cooling fins\u003cbr\u003e - High compression piston with rings, pin, \u0026amp; clips\u003cbr\u003e - Crankcase and clutch cover gaskets\u003cbr\u003e - Head gasket kit\u003cbr\u003e - 26mm Carburetor and intake kit\u003cbr\u003e - Jet kit with 10 different sizes (kit not pictured - recommend starting with a #100 or #105 with the 117 kit)\u003cbr\u003e - Throttle Cable\u003cbr\u003e - Air Filter\u003cbr\u003e\u003cbr\u003e \u003cstrong\u003eWill fit the following bikes, must already have our 88cc Race head kit installed:\u003c\/strong\u003e\u003cbr\u003e - Z50 (1992-1999)\u003cbr\u003e - XR50 (2000-up)\u003cbr\u003e - CRF50 (2000-up)\u003cbr\u003e - XR70 (2002-up)\u003cbr\u003e - CRF70 (2004-up)\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIMPORTANT NOTES:\u003c\/strong\u003e\u003cbr\u003e -As with all 117cc kits on the market, installation requires engine disassembly and case boring. Therefore, we highly recommend a professional technician install this kit and the cases bored by a reputable machine shop. If you plan on installing the kit yourself, you will need to have a Clymer or Honda shop manual. Instructions do not come with the kits but the installation of the crankshaft is just like installing a stock Honda crankshaft and both manuals cover this.\u003cbr\u003e\u003cbr\u003e \u003cstrong\u003eThe following parts should be installed at the same time as this kit.\u003c\/strong\u003e They are \u003cstrong\u003eNOT\u003c\/strong\u003e included:\u003cbr\u003e - High volume oil pump\u003cbr\u003e - Oil Cooler (we do not carry these at the moment)\u003cbr\u003e - Performance Cdi Rev box\u003cbr\u003e - CR8HSA spark plug (not required, but recommended)\u003cbr\u003e\u003cbr\u003e - If you have one of our Manual Clutch kits, there has been no long term testing to see how it will hold up to the additional power of this 117cc kit. If you use an inner rotor kit with manual clutch on 108cc or above, it can lead to premature clutch failure due to extra fatigue on the clutch housing. Also, do not tighten the clutch nut with a hammer and screw driver - it must be torqued on!\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236488159489,"sku":"4448A25","price":569.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8508.jpg?v=1780778342"},{"product_id":"yamaha-pw50-big-bore-kit-60cc-with-head","title":"Yamaha PW50 Big Bore Kit 60cc With Head","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing 60cc Big Bore Top End Kit with Head Included for Yamaha PW50 \u0026amp; QT50 Pit Bikes\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e Bolt on 60cc Big Bore Kit for Yamaha PW50 and QT50 Pit Bikes. Ready to install out of the box, includes all gaskets and components necessary to rebuild your top end. Our kits are complete, high quality and will extend the life of your toys for many more years of enjoyment. This kit can be installed by anyone with basic mechanical skills that is not afraid to turn some nuts and bolts. Breathe new life into your bike with our high quality, affordable and reliable big bore kit!\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eKit Includes:\u003c\/strong\u003e\u003cbr\u003e - 1 Cylinder\u003cbr\u003e - 1 Cylinder Head\u003cbr\u003e - 1 Piston\u003cbr\u003e - 2 Piston Rings\u003cbr\u003e - 2 Circlips\u003cbr\u003e - 1 Piston Pin\u003cbr\u003e - 1 Head Gasket\u003cbr\u003e - 1 Base Gasket\u003cbr\u003e - 1 Pin Bearing\u003cbr\u003e - 4 Cylinder Studs\u003cbr\u003e - 4 Stud Nuts\u003cbr\u003e - 1 Spark Plug\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits the following Yamaha models:\u003c\/strong\u003e\u003cbr\u003e PW50 Y-Zinger Peewee 50 (1981-2018)\u003cbr\u003e QT50 Yamahopper (1979-1987)\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236796473601,"sku":"4449B1","price":89.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/6909.jpg?v=1780790323"},{"product_id":"high-volume-oil-pump-vintage-honda-69-81-z50","title":"High Volume Oil Pump - Vintage Honda 69-81 Z50","description":"\u003cp\u003e\u003cstrong\u003eHigh Volume Oil Pump - Vintage Honda Z50\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e High volume oil pump for vintage Honda pit bikes and small ATVs. Delivers up to 3x the volume as the stock pump. We highly recommend upgrading your oil system when installing a big bore kit. Installation requires a 2mm drill-out of the oiling outlet.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits:\u003c\/strong\u003e\u003cbr\u003e - Z50 (1969-1981)\u003cbr\u003e - CT70 (Up to 1981)\u003cbr\u003e - SL70 (Up to 1981)\u003cbr\u003e - XL70 (Up to 1981)\u003cbr\u003e - ATC70 (Up to 1981)\u003cbr\u003e - TRX70 (Up to 1981)\u003cbr\u003e\u003cbr\u003e ** Note - Installation requires a 2mm drill-out of the oiling outlet.\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236802208001,"sku":"5122","price":32.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/5091.jpg?v=1780790554"},{"product_id":"88-up-honda-50-stage-2-big-bore-kit-z50-xr50-crf50","title":"88-Up Honda 50 Stage 2 Big Bore Kit - Z50 XR50 CRF50","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing Stage 2 88-Up Honda 50 Big Bore Kit for Z50XR50R and CRF50F\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003e Our 50 Caliber Racing Stage 2 Big Bore Kits are top quality and come with everything you need to finish the job. This is a great way to pump up your Honda Z50, XR50 or CRF50. This kit is recommended for those who don't want to spend a fortune but still want to see a nice power increase over the stock engine. It can be installed by anyone with basic mechanical skills who isn't afraid to turn some nuts and bolts.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIncludes:\u003c\/strong\u003e\u003cbr\u003e - Lightweight aluminum cylinder with steel sleeve\u003cbr\u003e - Cast in mounts on cylinder for aftermarket skid plates\u003cbr\u003e - Oversized cooling fins on cylinder for efficient heat dissipation\u003cbr\u003e - High compression 52mm piston with rings, pin, \u0026amp; clips (you can still run pump gas)\u003cbr\u003e - Head gasket kit, all gasket included needed for install\u003cbr\u003e- 20mm Performance carb assembly. Includes: 20mm carb, intake, heat stop, gaskets, mounting\u003cbr\u003ehardware\/wrench and air filter\u003cbr\u003e- Extended throttle cable (to fit aftermarket hand throttle)\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits:\u003c\/strong\u003e\u003cbr\u003e HONDA\u003cbr\u003e - Z50 (1988-1999)\u003cbr\u003e - XR50 (2000-Present)\u003cbr\u003e - CRF50 (2000-Present)\u003cbr\u003e\u003cbr\u003e *High volume oil pump is recommended\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236809613569,"sku":"4447","price":269.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8712.jpg?v=1780790781"},{"product_id":"honda-z50-performance-camshaft-1968-1981","title":"Honda Z50 Performance Camshaft 1968-1981","description":"\u003cp\u003e\u003cstrong\u003e50 Caliber Racing Performance Camshaft for Vintage Honda Z50 Pit Bikes and 70cc ATVs\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThis is a much more aggressive camshaft compared to the stock. Will increase power on a stock engine, and even better power can be made with a big bore modified engine up to 88cc. Works with a stock head.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003cstrong\u003eFits:\u003c\/strong\u003e\u003cbr\u003e - Z50 (1969-1981)\u003cbr\u003e - CT70 (Up to 1981)\u003cbr\u003e - SL70 (Up to 1981)\u003cbr\u003e - XL70 (Up to 1981)\u003cbr\u003e - ATC70 (Up to 1981)\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236812824833,"sku":"5640","price":60.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/7888.jpg?v=1780790876"},{"product_id":"108cc-stroker-kit-1-for-honda-crf50-xr50-crf70","title":"108cc Stroker Kit 1 for Honda CRF50, XR50 \u0026 CRF70","description":"\n\u003cp\u003e\u003cstrong\u003e50 Caliber Racing 108cc Stroker Kit #1 for Honda CRF50, XR50, CRF70, XR70 Pit Bikes\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003eReady for more power? Designed as a next-stage upgrade from our 88cc Race Head Big Bore kit, this kit will increase displacement to 108cc and adds approximately 2 horsepower. All the components are made specifically for 1988 and newer engines so there will be no fitment issues and no boring of the case necessary. A Honda engine upgraded with this kit will make much more power than Chinese Honda clones up to 125cc.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eKit includes:\u003c\/strong\u003e\u003cbr\u003e- 51mm Crankshaft\u003cbr\u003e- 24mm Carburetor (will fit the intake included with our 88cc kits)\u003cbr\u003e- Crankcase and clutch cover gaskets\u003cbr\u003e- Head gasket kit\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eWe recommend the following items be installed along with this kit. They are not Included:\u003c\/strong\u003e\u003cbr\u003e- High volume oil pump\u003cbr\u003e- Oil Cooler\u003cbr\u003e- Performance Cdi Rev box\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits the following Honda Pit Bikes:\u003c\/strong\u003e\u003cbr\u003e- XR50 (1988-up)\u003cbr\u003e- CRF50 (1988-up)\u003cbr\u003e- XR70 (1988-up)\u003cbr\u003e- CRF70 (1988-up)\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003ePlease note:\u003c\/strong\u003e\u003cbr\u003e-Installation requires the engine case to be split. You will need a Honda manual and proper tools to complete install. We highly recommend having a professional shop install this kit as it does not come with installation instructions and is very technical.\u003cbr\u003e\u003cbr\u003e- This kit requires a 52mm race head big bore kit. If you have not already upgraded, we offer a complete Stroker Kit #2 that includes all necessary parts to convert a stock engine to a 108cc race head engine, search our store for part # 4448A3.\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236966637825,"sku":"4448A2","price":275.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/3379.jpg?v=1780803099"},{"product_id":"high-volume-oil-pump-honda-pit-bikes-1982-up","title":"High Volume Oil Pump - Honda Pit Bikes 1982-Up","description":"\n\u003cp\u003e\u003cstrong\u003e50 Caliber Racing High Volume Oil Pump - Honda Pit Bikes CRF50 XR50 CRF70 XR70\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003eHigh volume oil pump for Honda 50cc Pit Bikes. Delivers up to 3 times the flow of the stock pump, which will help reduce wear and prolong the life of your engine. This pump is highly recommended when installing a big bore kit. Includes pump and gasket.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFeatures\u003c\/strong\u003e:\u003cbr\u003e- Prolong the life of your engine\u003cbr\u003e- Recommended when installing big bore kit\u003cbr\u003e- Pump and gasket included\u003cbr\u003e- Delivers 3x the volume of stock pump\u003cbr\u003e- Requires 2mm drill out of oiling outlet\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eFits the following Honda pit bikes:\u003c\/strong\u003e\u003cbr\u003e- Z50 (1982-1999)\u003cbr\u003e- CT70 (1982-1994)\u003cbr\u003e- XR50 (2000-2003)\u003cbr\u003e- CRF50 (2004-2023)\u003cbr\u003e- XR70 (1997-2003)\u003cbr\u003e- CRF70 (2004-2023)\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e*Note:\u003c\/strong\u003e Installation requires 2mm drill out of oiling outlet\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236966998273,"sku":"5121","price":26.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/6695.jpg?v=1780803112"},{"product_id":"117cc-stroker-kit-5-for-honda-crf50-xr50-crf70","title":"117cc Stroker Kit 5 for Honda CRF50, XR50 \u0026 CRF70","description":"\n\u003cp\u003e\u003cstrong\u003e50 Caliber Racing 117cc Stroker Kit #5 for Honda CRF50, XR50, CRF70, XR70 Pit Bikes\u003c\/strong\u003e\u003cbr\u003e\u003cbr\u003eContains everything you need to convert your 88cc Race Head engine into a powerful open class 117cc engine (much more powerful than the common Chinese 107 and 125cc engines) with tons of torque! Also, this crank was made specifically for the newer engines and thus, you will not have any fitment issues like trimming the piston skirts in order to clear the crank or the piston not lining up with the cylinder deck.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eKit includes:\u003c\/strong\u003e\u003cbr\u003e- 51mm Crankshaft with NTN Bearings\u003cbr\u003e- Lightweight 54mm aluminum cylinder with steel sleeve, cast in mounts for skid plates, and larger cooling fins.\u003cbr\u003e- High compression piston with rings, pin, \u0026amp; clips\u003cbr\u003e- Crankcase and clutch cover gaskets\u003cbr\u003e- Head gasket kit\u003cbr\u003e- 26mm Carburetor and intake kit\u003cbr\u003e- Jet kit with 10 different sizes (kit not pictured - recommend starting with a #100 or #105 with the 117 kit)\u003cbr\u003e- Throttle Cable\u003cbr\u003e- Air Filter\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eWill fit the following bikes, must already have our 88cc Race head kit installed:\u003c\/strong\u003e\u003cbr\u003e- Z50 (1992-1999)\u003cbr\u003e- XR50 (2000-up)\u003cbr\u003e- CRF50 (2000-up)\u003cbr\u003e- XR70 (2002-up)\u003cbr\u003e- CRF70 (2004-up)\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003eIMPORTANT NOTES:\u003c\/strong\u003e\u003cbr\u003e-As with all 117cc kits on the market, installation requires engine disassembly and case boring. Therefore, we highly recommend a professional technician install this kit and the cases bored by a reputable machine shop. If you plan on installing the kit yourself, you will need to have a Clymer or Honda shop manual. Instructions do not come with the kits but the installation of the crankshaft is just like installing a stock Honda crankshaft and both manuals cover this.\u003cbr\u003e\u003cbr\u003eThe following parts should be installed at the same time as this kit. They are \u003cstrong\u003eNOT\u003c\/strong\u003e included:\u003cbr\u003e- High volume oil pump\u003cbr\u003e- Oil Cooler (we do not carry these at the moment)\u003cbr\u003e- Performance Cdi Rev box\u003cbr\u003e- CR8HSA spark plug (not required, but recommended)\u003cbr\u003e\u003cbr\u003e- This kit requires an 88cc race head kit to already be installed. If you have not already upgraded, we offer a complete Stroker Kit #6 that includes all necessary parts to convert a completely stock engine to a 117cc race head engine, just enter part # 4448A25 in the search box at the top. \u003cbr\u003e\u003cbr\u003e- If you have one of our Manual Clutch kits, there has been no long term testing to see how it will hold up to the additional power of this 117cc kit. If you use an inner rotor kit with manual clutch on 108cc or above, it can lead to premature clutch failure due to extra fatigue on the clutch housing. Also, do not tighten the clutch nut with a hammer and screw driver - it must be torqued on!\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":49236967063809,"sku":"4448A24","price":419.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0816\/8256\/3329\/files\/8507.jpg?v=1780803128"}],"url":"https:\/\/utvdude.com\/collections\/pit-bike-big-bore-kits.oembed","provider":"UTV Dude","version":"1.0","type":"link"}