grub2 - 2 linux partitions, how to force one's grub menu to win?

I have 2 Ubuntu partitions

• Ubuntu 14.04 that is my desktop system


• Kubuntu 14.04 that is my development enviroment

Each time Ubuntu 14.04 updates the kernel, writes his own grub menu, and each time Kubuntu 14.04 updates the kernel, writes his own grub menu

When Kubuntu 14.04 has written his own grub menu, how can I force Ubuntu 14.04 to gain again control of the grub menu (and I suppose of the MBR)?

Boot back into Ubuntu and run

sudo dpkg-reconfigure grub-pc

this will reconfigure grub based on the partition where you are,
after this you could run

sudo update-grub 

and it will update the menu defaulting to itself.