Intel Z370 motherboards do not support Kaby Lake CPUs
 

Only for Coffee Lake CPUs

As some of the first Coffee Lake samples have reached reviewers it was just a matter of time before someone tried to run a Kaby Lake CPU with the new Z370 chipset based motherboard, and it does not work, at least not yet.

http://fudzilla.com/news/motherboard...kaby-lake-cpus