good lord... how rich was this thing running? All those black deposits are from either running REALLY rich, cheap lubricants, or both. I'm betting both. As we all know, solids and liquids arent compressable like gasses are. So, the parafen (wax lubricant) deposits built up on the crank, top of the piston, cylinder head button, glow plug, etc. Compounded by the excess (unburned) fuel and lubricant in the combustion chamber, reduced the compressable volume. This increased the compression ratio and placed more stress on the conn rod, resulting in catastrophic failure.

BTW black deposits like that are from running too rich or to cool. Running too hot results in white ash or a rainbow discoloration of the metal parts, depending on the alloy used.

Just goes to show the importance of taking your time to get the tune right.