It stopped with a bang! Broke a valve.

[The Buddha]

In my case it was a tight guide and/or valve stem material not made with a inherently resistant material to galling like inconel and a dumbass rider who never paid attention to it. There are some precautions ... good oil, syntehtic preferably and maybe warming up the bike before jumping on it and taking off ... etc ...
Cool.
Srinath.

[Sprinklerhead]

I snapped a valve before.  Managed to kill the engine in my GSXR 750 when I did it.  The valve and the piston turned into shrapnel pretty fast.  I later found most of the piston sitting below the clutch basket.  I was probably doing about 70 mph when it happened.  It's a funny feeling seeing smoke coming up over the front of the tank on the freeway.

Photos

[The Buddha]

Man that was some severe damage. Mine had a couple of bits of aluminum in the alternator cover ... and the bottom end looks like it was nearly un impacted. Rod looks good, dont shake at all, pin looks fine ... maybe cos my piston was nearly intact ... OK many surface impacts and a little piece missing ... but otherwise OK. See a single cylinder ... when you hole one piston ... you sorta limit your ability to damage stuff ... You had 3 cylinders helping this one self destruct ...
Cool.
Srinath.