Fitment: 2014-Current Honda CRF125F & CRF125FB TB Parts 138cc big bore kit for the Honda CRF125. This will make your trail bike a lot more fun to ride by adding some much needed power. With the larger bore, this bolt-on upgrade kit will give you more power and higher compression for a very reasonable price. This kit does not require boring of the case – simply bolt on, tune (Not included) and go!! This is an ideal option if you’re looking to add some power or you just need a new cylinder, piston, and rings to rebuild your engine. Key features: High quality, high compression 55mm piston, with rings, pin, & clips 11.0:1 compression ratio compared to Stock 9.0:1. Our piston is pump 91+ octane gas friendly. Aluminum cylinder with steel sleeve (55mm) Head gasket kit with exhaust gasket! Largest bore you can go without boring the cases More power and fun at an affordable price Easy bolt-on kit +2.6mm of bore or 13cc 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 having a professional technician install this kit or, at a minimum, purchasing the shop manual for your bike. We also have a link on our website in the INFO section under Honda where you can find additional info. The parts are installed in the same manner as the OEM parts. Notes: Fuel Injected models – Tuning Required the ECU will require a flash/tune to prevent a lean condition and possible damage to your engine. CJR Performance (cameronjonesracing.com) provides this service and can also adjust the tune based on your other modifications. Serious fun for the small bore. Proudly made in the USA!Please keep in mind that 2019+ EFI models will require a fuel controller like the aRacer MiniX that we sell or an ECU flash from CJR in order to use this kit.