Big Bore Kits

50 Caliber Racing 88cc Race head kit for 88-up Honda 50 or 70cc pit bike. This kit will drastically improve your overall performance on your bike. A stock Honda 50 puts around 2.2hp to the ground and this kit will put you between 5.5-6hp 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!

50 Caliber Racing high volume oil pump for Honda pit bikes CRF50 XR50 CRF70 XR70. 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.

50 Caliber Racing Stage 2 88-Up Honda 50 Big Bore Kit for Z50 XR50R and CRF50F. 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.

88cc Race head big bore kit for your vintage Honda pit bike. Complete with a 52mm piston and cylinder, fully assembled race head with 25/22mm valves and revised chamber. 20mm carburetor with intake, filter and cable. High performance camshaft. Full gasket kit. Everything necessary to fulfill your need for speed!

- Z50A (1968-1978)
- CT70 (1969-1982)
- ATC70 (1973-1985)
- SL70 (1971-1973)
- XL70 (1974-1976)

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.

50 Caliber Racing Honda Z50 Stage 1 vintage big bore kit. Improved lightweight 52mm piston and cylinder design, with oversized cooling fins for efficient heat dissipation. Includes all gaskets needed for install.

- Z50 (1968-1978)
- CT70 (1968-1981)
- ATC70 (1973-1985)
- TRX70 (1986-1987)
- SL70 (1971-1973)
- XL70 (1974-1976)

The Stage 1 Big Bore Kit from 50 Caliber Racing is top quality and comes 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.

50 Caliber Racing vintage stage 2 88cc big bore kit. Improved lightweight 52mm piston and cylinder design, with oversized cooling fins for efficient heat dissipation. A 20mm performance carb assembly, and all the gaskets needed for install.

- Z50 (1968-1981)
- CT70 (1968-1981)
- ATC70 (1973-1985)
- TRX70 (1986-1987)
- SL70 (1971-1973)
- XL70 (1974-1976)

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.

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 XR70 or CRF70. This kit will easily double the stock horsepower on your bike. We recommend installing a high volume oil pump with this kit.

50 Caliber Racing Performance camshaft for vintage Z50 Honda pit bikes and 70cc ATVs. This 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.

50 Caliber Racing High Performance Camshaft with much more aggressive lift and duration. Increase power with a simple camshaft change. Goes well with big bore kits and aftermarket CDI. Fits Honda CRF50 and CRF70 pit bikes.

50 Caliber Racing 108cc Stroker Kit #2 for Honda CRF50, XR50, CRF70, XR70 pit bikes is 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 & 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 an additional 2 horsepower over a standard 88cc race head kit.

50 Caliber Racing 108cc stroker kit #1 for Honda CRF50, XR50, CRF70, XR70 pit bikes adds approximately 2 horsepower over your stock setup! 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.

50 Caliber Racing 117cc stroker kit #6 for Honda CRF50, XR50, CRF70, XR70 pit bikes. Contains everything you need to convert your completely stock engine into a powerful open class 117cc engine with tons of torque. Includes crank, race head, camshaft, cylinder, piston kit, gaskets, 26mm carburetor and intake kit.

50 Caliber Racing 108cc stroker kit #5 for Honda CRF50, XR50, CRF70, XR70 pit bikes. Contains everything you need to convert your 88cc Race Head engine into a powerful open class 117cc engine with tons of torque. Includes crank, cylinder, piston kit, gaskets, 26mm carburetor and intake kit.

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