An STK file contains stock calibration information used by Dynojet Power Vision to transfer, or "flash," information to Harley-Davidson motorcycles that tunes various components to improve performance. It stores calibration data for how the motorcycle should run, such as the RPM limit, idle RPM, and throttle blade control. STK files also contain information about the motorcycle, such as the year, make, model, and VIN.
Dynojet Power Vision is a handheld tool that plugs into the data port of a motorcycle and is used to retrieve information from the motorcycle's computer system. The information is saved in the STK file, which can be opened by Dynojet Power Vision software in Windows. STK files are located in the "Stock Files" folder of the "Power Vision" installation folder.