Well I'm up to 158hrs on my 2016 350. No issues at all with the engine up to this point I've just pulled it down to do a top end rebuild. The rings are still in spec as is the piston could have left it to 200hrs easy. Its a major pain to do the top end you have to pull the engine from the frame and its one of the hardest bike engines I've ever pulled out, you have to hold your tongue just at the right angle and its heavy or I'm old and weak. The valves are still in spec which I'm very happy and relived with. This Beta is Yamaha reliable for a 4st.
Bit of a disclaimer about me and my riding style! I don't rev it to the limiter very often and I'm sure as hell not one of the guys sitting on the start line smacking off the limiter. I ride the bike in the fat part of its power in the upper midrange I'm sure this is reflected in the engine life. Air filter every ride and I clean the airbox as well, engine oil every second ride and a filter every second oil change. Will post up some pics later for anyone who is interested. One other thing the rings SUCK so much tension and you have to use a ring compressor also the piston clips are made of Hercules's hair very tough. Forgot also did the cam chain it is also in good nick.
MM
ps will put this on a few forums people need to know these things are bomb proof.