This Yamaha 200cc air cooled motor had mechanical noise from cylinder head. So, we checked and found the reason, here.
This motor made 19000 mile by street ride. It may happen but we never saw this part worn out like this. It is dented.
Not sure what the cause but probably multiple reasons. What we can do to avoid this trouble is just keep motor oil maintenance and valve clearance adjusted. We'd recommend oil change every 3000 miles or less (for street use).
Air cooled motor temperature will not be as stable as water cooled motor. That means little harder for oil. So, choose better grade oil for your motor.
We replaced valve adjust screw and adjusted clearance Intake and Exhaust side again. Good to go without noise!
Furuhashi Racing would maintain your street bike specializing in metric here in Indianapolis, IN. Let us know if you have any questions.
Have a nice ride!
