https://www.dropbox.com/s/97tnt44i1f5i9ol/ntrboot_r4i-sdhc.com.rar?dl=0 may work (the nds-backup file). It's from the r4i 3ds b9s but they have the same hardware if your r4 isn't too old. But you should try to make a flash backup first.
how can i use this? where to put? on root? tnx. (by the way i already tried the one on the 1st page downloaded. but nothing happens)