Here is the big bore kit proposed by ATHENA to increase the capacity of your motocross / enduro YAMAHA YZ 250cc from 2003 to 2021. This kit in Ø72mm against Ø66mm of origin thus makes it possible to pass your motor bike of 250cc has 294cc real! A gain of torque and performance will be immediately felt. It allows a gain of 4 HP on average which is huge on this vehicle. You go from 41hp to 45.3hp thanks to the high engine ATHENA BIG BORE. Enough to have fun on the tracks or in the forest. ATHENA has also planned things well because this top engine is sold complete. It includes the cylinder, piston, ring, cylinder head and all the gaskets you need for a quality and tight reassembly. The advantage of taking this engine is that it is designed to be mounted on the original connecting rod, so you have no modification to do! Attached is the power curve so that you can see for yourself the difference between the original and the big bore. We have also provided you with the assembly instructions if you wish to have more information on the assembly of this kit for example the adjustment of the squish. You will also find a detailed list of vehicles on which this cylinder can be mounted.

Fits on:

YAMAHA YZ 250 (CG13) 250 2003

YAMAHA YZ 250 (CG17) 250 2004

YAMAHA YZ 250 (CG20) 250 2005

YAMAHA YZ 250 (CG23) 250 2021

YAMAHA YZ 250 (CG23) 250 2020

YAMAHA YZ 250 (CG23) 250 2019

YAMAHA YZ 250 (CG23) 250 2018

YAMAHA YZ 250 (CG23) 250 2017

YAMAHA YZ 250 (CG23) 250 2016

YAMAHA YZ 250 (CG23) 250 2015

YAMAHA YZ 250 (CG23) 250 2014

YAMAHA YZ 250 (CG23) 250 2013

YAMAHA YZ 250 (CG23) 250 2012

YAMAHA YZ 250 (CG23) 250 2011

YAMAHA YZ 250 (CG23) 250 2010

YAMAHA YZ 250 (CG23) 250 2009

YAMAHA YZ 250 (CG23) 250 2008

YAMAHA YZ 250 (CG23) 250 2007

YAMAHA YZ 250 (CG23) 250 2006