The Yamaha GYTR Power Tuner (part No. 33D-H59C0-V1-00, retail $279.95) is a handheld unit that allows the user to create custom maps without a PC or 12-volt battery source. Instead, it is powered by two AA batteries. The GYTR tuner is far and away the easiest and most practical unit for creating custom maps. It plugs into the wire harness behind the left-side shroud. By using nine adjustment points to change both fuel mixture and ignition timing, fuel mixtures can be varied up to 14 percent rich or lean, and ignition timing can be advanced up to 4 degrees and retarded up to 9 degrees. The memory can store nine maps at a time and it can read your current map if you forget what you programmed. There is a monitor setting that allows the user to see engine run time, engine temperature, and also run a self-diagnosis. The same tuner will work on 2010–’14 YZ450Fs, 2014 YZ250Fs, and 2013–2014 WR450Fs.