HELP- my PX has died

[bobdylan]

While I was riding today I heard a pop and my bike cut out and wouldn't restart. I've tried a new spark plug but still no avail, the bike is turning over but not kicking in, and I think I can hear a bit of a whistle from the fly wheel while trying to start it. The carb seems fine, and there is plenty of fuel n oil in.
Has anyone got any ideas what it could be or point me in the right direction.
Thanx

[scootlin]

sounds to me like uve holed ur piston! sorry. put ur hand over ur exhaust and kick it over, if there is no compression, then its likely!