Where I ride KTMs and Hondas are common, Yamaha's are somewhat rarer. I do not know any local owners to ask so I thought to post here.
My local shop (which sells gear and repairs bikes but is not a dealer) advised against a new 450 Yamaha on the basis that two other customers have had stretched timing chain issues. One guy allegedly even required a replacement at 10 hours on his new 2015. Both riders ride in the desert, spending hours at high RPM. Apparently, the replacement timing chains quickly stretched as well.
Has anyone had issues with this? The magazines call the yz450f bulletproof; searches on the web do not turn up pages of stories on timing chain failures on new reverse slant cylinder yamahas. If this was a major worldwide issue, there would be lots of info available (and likely Yamaha would have redesigned the tensioner for 2016 which they did not).
FWIW, I only ride MX and was considering a 2016 450. I did test ride a 2014 in the past and loved the suspension and the torque. I think I will need to grow into the handling (my current bike is a KTM 250 SX 2 stroke so any 4 stroke seems weird at first).