The KTM 450 SX-F is on top of the world coming into 2019. It has won six national championships in six years, and it’s generally considered the bike to beat in racing everywhere. What happened? Relentless change, that’s what. Even when it seemed that change was unnecessary, the KTM has continued to morph and evolve. This year’s bike is a perfect example. Despite all its success, the KTM 450SX-F has dramatic changes for 2019. WHAT’S NEW AND WHY The 2018 450 was already the lightest and fastest bike in the class, but the others are catching up fast. A few years ago KTM had the only electric-start bike in the 450 class....