kernel_task is the core of OS X. It runs all the device drivers, and other high privilege tasks. If it’s spiking up like that, it could be a bad device driver causing it. Have you checked the logs to see if anything is being reported there? Also, have you installed any 3rd party USB drivers (including printers, scanners, etc) as they are often a cause of problems

Over the last few days I experienced a strange bug that didn�t go away even after several times of rebooting � a process called syslogd used up to 100 percent of one CPU, which means up to 50% of my computer�s processing power.

After some research, I found the following solution:

Fire up Terminal and execute the following commands (enter administrator password when asked):

sudo launchctl stop com.apple.syslogd
sudo rm /var/log/asl.db
sudo launchctl start com.apple.syslogd

What do these commands do? First of all, we stop the syslogd process. The second line removes a database file which causes the whole dilemma (don�t worry, it�ll be re-created afterwards), the third line starts the previously stopped process again.

With a hyperactive kernel_task, check the fonts and font cache.