Looks mostly like K2 to me. The K2 had the dipped-ribbed sides on the seat, with the seat narrowed right there (like mine!). The tank has the slightly flattened areas where the decals went, too.
The sidecovers on K3 had the K2 indents, but the larger K3 logo on them, which frequently broke off from legs dragging over them during takeoffs. So, it could possibly be K3, but the engine looks too well formed: the K3 has the worst-cast engines, usually showing up on the fin edges and the top of the crankcase (as wrinkles). The K2 still had pretty good quality control.