Yamaha YZ400 YZ426 YZ450 4 Stroke Performance Jetting Pilot Main Carb Stage 1-7 Jet Kit Increased Performance at all RPM's, Faster Throttle Response, & Stops Lean Exhaust Popping that Damages Engines. Each Jet Kit is Custom Made to your Specifications for Optimum Performance, When You Order, Please EMAIL US FIRST through Amazon with Your Exact Year, Model, Modifications Made, & Elevation, So we can Design, Build, & Ship Your Kit. The kit comes with complete instructions for installation. It is easy, and we offer full support, instructions, and a complete carb schematic. Only basic hand tools are required. Kit Includes: Main Jets, Pilot Jet, Leak Jet, Needle Adjusters, Nylon Spacers, Drill Bits, Slide Hole mod (with CV carb), Idle Mixture mod, Slide Spring Mod (with CV carb), Carb Schematic, Specifications, Carb Sync Tool build, Carb Cleaning Procedure, Proper Tuning Techniques, and step by step instructions with photos. We give a 100% Satisfaction Guarantee. Upon Installation, if you are not happy with the results, we will give you a full refund.