These carburetor tuning kits from Dynojet are the best solution for eliminating the flat spots in the acceleration of Sportster and Big Twin 1988 to present equipped with Keihin CV carburetors. Dynojet kits permit easy tuning of the carburetor on stock motors as well as motors with performance cams and exhausts. Each kit comes with a detailed easy-to-read instruction book that leads you step-by-step through the carburetor tuning and modification. Also included are a selection of main jets, a needle jet, an adjustable needle with spacers and circlips, a spring and drill bits.