Only had our 1300A just under 18 months but I did notice that the rear brake never seemed to release completely and by the sound I could hear though it didn't take long for the sound to disappear.
Early in October while having the rear tyre changed over I greased up the caliper which being the same as our 1100A was somewhat harder to separate. Greased up the all the pins and after put it all back together and went for a ride.
The sound I could here from the rear and gone away so I put it down to lack of maintenance on the calipers causing them to stick.
At the moment the front wheel is off but it did take some effort to take both calipers off; it seemed the brakes were still slightly applied. I'd hazard a guess and say the grease on the calipers has dried out causing them not to release properly.
You may have a similar issue but the 1300 does tend to have issues with the secondary master cylinder which is above the LH caliper as well. Maybe not so common is a broken return spring in the pedal master.
Someone with more 1300 knowledge might be able to help better.
