Yes, delete means running the mke2fs again, then mount it and then do the tar thing again. make sure you use GNU tar, not the default busybox tar. Also use the kernel with fast mmc speed and multiblock writes enabled, tar copy is a good test to check if that kernel is stable (and the copy will run much faster too). Don't forget to run umount before rebooting. If the copy still doesn't work, run the tar line without 'v', it should print only errors and there should be only one warning on the end about old timestamp. Also check kernel log via 'dmesg' command after copy is done, you shouldn't see any I/O errors there.