TB 120cc Bore Kit w/Cam Chain – XR/CRF100 TBparts 120cc big bore kit with cam chain. For all Honda XR/CRF100. High quality and high performance! Our 58mm big bore piston will add more power! Matched with an aluminum cylinder with a strong cast in place steel sleeve. This also makes a great stock replacement option as it cost less than an OEM rebuild. Safe with pump fuel 91+ octane too! 120cc XR100 & CRF100 Big Bore Performance Kit (58mm):  Aluminum cylinder with steel sleeve High compression 58mm piston with rings, pin, & clips Head gasket kit New Cam Chain This affordable 120cc Big Bore Kit will make your XR100 or CRF100 a lot more fun to ride by adding some much needed power. This kit does not require boring of the case – simply bolt on and go!! 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 the Clymer’s repair manual or something similar. The parts are installed in the exact same manner as the stock Honda parts.