How many hrs on cam chain , if it sitting high on the cam sprockets replace , any links kinked replace it, these engines are reliable if you keep fresh oil and filter maintanance , of course top end intervals are govered by how hard you ride and i dont mean just the piston and ring package , pay attention to valve wear , spring length , bucket wear , seat and guide wear etc , anything looks suspect replace ,i dont know how many hrs your 13 model has done but on our bikes 2 and 4 stroke we have set hrs we do on them than they come apart if they need it or not ,same with shocks and forks , linkage etc.
