Originally Posted by mikeysduck
2011 vs. 2013 I was pondering the same question.
I thought the 2012 had significant motor updates.
2011 there was no 350 EXC-F. It was introduced in 2012 with the brand new designed engine. Compared to its big 450 brother it has two camshafts and all valves are titanium, the engine case is new and has only two oil pumps and no seperated oil circuits.
The 2013 has, as far as I know only the technical updates which have been installed on the 2012 models after some problems. Rubber throttle potentiometer cover, easier to replace and better fuel filter and stuff like that. And the "Six Days" bike has a new fork.
Edit: the 2013 has a new designed balance shaft and a new starter and starter gear.