I have the same problem with my explorer. Here is what I tried and this worked fine for a long time.
1. Install the app "Link2SD" after rooting the phone.
2. Move the big apps like Maps, Facebook etc to the SD card.
3. Also you can delete those unwanted stock apps without any fuss.
Now I have only 5 apps on the internal memory, one of which is Gmail which I could not move. I keep getting some error. And all new apps that I download were automatically getting installed in the SD card.
The above worked smoothly for a few months, then again the space problem has started. Gmail does not sync when the internal space is low. I tried deleting all data in gmail and now when I open Gmail I get the message 'waiting for sync', ' Your email will appear shortly'. But nothing happens. Can someone help please ?