Stratwhak shared this story of mystery metal in his 1995 XL883 conversion:

I was heading home from work and the engine dies on me at 45mph. I pop the clutch and it fires right up. Came to a stop and the engine sounds great. I go another 5 miles down the road running 60, engine starts rattling like crazy and dies again. I trailer the bike home and start trouble shooting. Took the plugs out and tried to roll the bike in gear, wouldn’t budge. Took the primary cover off and eyed the tranny over, it’s fine. Took the timing cover off, gears are in great shape. Put the bike in neutral and I was able to turn the engine backwards with the crankshaft nut but it would stop when the rear piston was at TDC. Finally a clue! Pulled the rear head and found a small piece of metal sitting on top of the cylinder.

Damage

Damage

More damage

Yes, the piece is magnetic

With the help of some good friends and the great guys at xlforum.net we went through the list of the usual suspects to source the metal, but all was OK.

This ring is complete

No scews missing from inside the carb

Another shot of the carb

Valve guide looks good

No, the ground electrode did not break off the spark plug

Then they finally got through to me that shrapnal can and will cross over through the intake manifold. Dude! Pull the front head already! Doh!

The culprit

Ouch

Looks expensive

Now for the $64,000 question: what happened and why?