OK here we go with the tutorial....
1, Install Root Too from here...
https://www.windowsphone.com/en-us/store/app/root-tool/f4acc009-ea1e-4063-9bab-fec50195aa1e
2, Move it to SD card.
3, Put the SD card in the memory card reader and go to WPsystem folder
4,Delete the following two files from the installation path..
sdcard\wpsystem\apps\f4acc009-ea1e-4063-9bab-fec50195aa1e> install
mdilfilelist.xml and wmappmanifest.xml
5, Move all the files under folder HACK to installation path..
sdcard\wpsystem\apps\f4acc009-ea1e-4063-9bab-fec50195aa1e> install
6, Move the app back to phone memory.
7, Run the Root Tool app
8, Open
Lumia Registry Editor
9, Selcet
HKEY_LOCAL_MACHINE
10, Select
DWORD
9, In the path type
System\maps\storage
10, In the Key type
UseExtendedStorage
11, Press
Read
12, it will show
00000000 in the value field
13, Change the value to
00000001
14, Press
Write
15, In the
Key field type
UseSmallerCache
16, Press
Read ensure it reads as 00000000 if not change it to 00000000 and press
Write
17, In the
Key field type
ExternalStorageOverride
18, Press
Read. ensure it reads as 00000001 if not change it to 00000001 and press
Write
19, Go tot the maps and download a new map.
20, Go to Storage Sense and select SD Card
21, Maps session should show the maps size you have just downloaded.
I thank
djamol from XDA forum for the wonderful
Root Tool.