They fit the k1300s. And GT.
You need to have the pistons fully pushed back and the caliper need to be able to fully float on the hanger it sits from, in the front the calipers are fixed and the disc float, in the rear the caliper floats and the disc is fixed. It is not uncommon for the caliper to get stuck due to corrosion and dirt on the pins on wich it should float, take it all apart and really clean it, also the holes in the caliper.
If all is ok with the caliper it doesent even need to be taken off for replacing pad's, just remove the retaining pin, push the caliper as far as can be towards the disc to seat the pistons, pull out old pads, in with the new and the retaining pin. done.
So it sounds like your pistons are still out a bit or the caliper.