Another pic

You have a piston overheating problem.  We need to check the cooling system, the fuel system, the exhaust system for proper operation.  Show me the spark plug or look at the porcelain insulator using a 2 to 5 power magnifying glass that surrounds the center electrode and describe what you see.    It is not a piston to cylinder wall clearance problem.  The failure is not related to the brand of piston or ring gap.

Does you bike have a spark arrestor type muffler?  If so ,does it have a screen or turbine type arrestor in the muffler? What type of exhaust system do you have?

Describe how you were riding it the last 30 seconds before it quit. 

I just noticed that you said you had a loose intake boot.  That may have cause the engine to run extremely lean lean at anything less than about 3/4 throttle position.  We still need to check the things mentioned above to make sure it does not do it again when you install a new piston.