2007 SX-f 450 engine issues

[canucklehead]

sorry for cross posting this. I originally posted in Supermoto (I thot that's what the SX-F is for). I think it'd be better asked here:

My son was riding his '07 450 SX-F and heard a nasty metal on metal noise, then it stopped running and wouldn't start. He described it as sounding like a bucket of bolts being shaken around in a blender.

Oil had been changed regularly with synthetic. Valves were just checked and within spec (altho tight end of spec). Prior to this we had a bit of a rattling sound (some might even call it a tick noise, but more of a rattle). My cousin has owned many KTMs and he said the noise was clutch basket, not top end. He said KTMs often had noisy clutch basket issues (at least his 525 & other models always do). Another person who knows nothing about KTMs thought that noise was top end/valve. The rattle noise could be coincidence, or related.

So where do I begin on this? Do timing chains let go? Compression test it?

thanks for your help.