Windows 8 doesn’t show up in my grub menu

I have two HD’s, one with Fedora 20, and the other with Windows 8.

I can choose at start up which drive to boot from, and choosing the one where I installed windows does make it start, but I would like to have the option in the grub menu instead of having to press F11 when my computers starts etc.

Here is the output of fdisk -l:

Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 1815802D-B749-4FD4-8297-EABE9FD93AE0

Device           Start          End   Size Type
/dev/sda1         2048       616447   300M Windows recovery environment
/dev/sda2       616448       821247   100M EFI System
/dev/sda3       821248      1083391   128M Microsoft reserved
/dev/sda4      1083392    976773119 465.3G Microsoft basic data


Disk /dev/sdb: 55.9 GiB, 60022480896 bytes, 117231408 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x000a4b0c

Device    Boot     Start       End   Blocks  Id System
/dev/sdb1 *         2048   1026047   512000  83 Linux
/dev/sdb2        1026048 117229567 58101760  8e Linux LVM


Disk /dev/mapper/fedora_5586577d00-root: 15.6 GiB, 16777216000 bytes, 32768000 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk /dev/mapper/fedora_5586577d00-swap: 5.6 GiB, 6002049024 bytes, 11722752 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk /dev/mapper/fedora_5586577d00-home: 34.2 GiB, 36712742912 bytes, 71704576 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

I have searched google for a solution, and several recommended running grub2-mkconfig -o /boot/grub2/grub.cfg but that doesn’t fix my problem, nothing changes.

How can I add Windows 8 to my grub menu?

Had this problem like 2 days ago,
Fixed by modifying /etc/grub.d/40_custom
Add as follows:

menuentry "Windows Vers" {
set root='(hdX,X)'
chainloader +1
}

Where hdX,X is your disk with windows, /dev/sda1 is hd0,0, /dev/sdb1 is hd1,0 and so on.

Then run grub2-mkconfig -o /boot/grub2/grub.cfg
Hope it will work for you the same, as it worked for me.