kernel_task problem

[needlen]

So here is my Problem, when downloading big files or unraring or Installing something, my process kernel_task is going into the loads its jumping around between like 60% and 99% making the Unrar Process for example or the Download extremly slow, i tried network transfer it had like 9mb/s for about 10 seconds, then kernel_task jumped up and slowed down everything to 2.6mb/s

 

anyone got the same problem and has an answer to this?

 

It is not Spotlight, i have disabled indexing on every volume.

 

thanks in advance