problem during kernel bootup after flashing a compiled one unmodified after cloning from google repositoy

I want to compile a kitkat kernel for nexus5(hammerhead) and i downloaded the source from google repository using GIT CLONE and followed the steps mentioned on the developer website(official). then i took a factory image of kitkat kernel(boot.img) and extracted initramfs.cpio.gz using "unmkbootimg" tool. which printed thow to remake the bootimg using "mkbootimg" by:

./mkbootimg --kernel zImage --ramdisk initramfs.cpio --base 0x26fff00 --cmdline 'console=ttyHSL0,115200,n8 androidboot.hardware=hammerhead user_debug=31 maxcpus=2 msm_watchdog_v2.enable=1' -o new_boot.img

after kernel was compiled using MAKE HAMMERHEAD_DEFCONFIG followed by make, i used mkbootimg to create a new_boot.img file. then restarted in bootloader mode and ran, ./fastboot boot new_boot.img

now the device got stuck at first GOOGLE screen *no adb running till now so no kernel messages. i didnt change anything after git clone,what i did was just compiled it, with default settings.