Athena (P400510100004) 83mm 290cc Big Bore Cylinder Kit Kawasaki KX 250 F 2004-2008; Suzuki RM-Z 250 2004-2006; Athena's Big Bore kit brings the raw power you have been missing in an easy to install, reliable package that bolts on with no machining needed in most cases, and includes easy-to-follow step-by-step installation instructions