Gt i9100 JB stock Kernel topic

Hi guys ! So , I have a SGS2 with JB stock rom ( XWLST - Indian rom ) rooted by flashing Speedmod kernel. I want to go back to the stock kernel . I searched in google but got no luck , so should I unroot the phone in superSu to get or reflash the rom ( tried but nothing happened ) or is there any link to download the stock kernel and flash it using odin ? Any ways for doing this thing ? Thanks :).