When I start the game it's running fine but once the world loads the CPU jumps from 6% to 95% and stays at 95% after world has generated. I will post a link to my world at the bottom so you can download and test it your self I tired to open a log file but I can't read it to see what is going on. This world is survival and I live in a village with villagers so maybe there reproducing to much which maybe causing it to lag.

http://tafaricraft.com/downloads/TzsBAAq3RgA=.zip