2007 Kymco Venox 250 "damage valves 4 timing chain" Questions

...damage was caused to piston and valves Was it just one rocker arm that broke or is the other damaged did the timing jump and piston hit open valves driving them up and breaking arm and damaging cam ...

...damage may have occured with the camshaft stopped and the crankshaft and piston still moving briefly. A cylinder leakdown test should confirm this issue. same problem, timing chain broke, replaced it ...

valves. There is a TDC mark on the flywheel on the left side under a plug. Pull the cover off the head at top on left side and check to see where the timing mark on the cam vs mark on the head are. If