would love to know why , I find the only brittle areas in the ali sculptures are where they have been tig welded , the KLR bash plate has formed grooves - to make the plastic form stronger , I could fill those and have thicker areas for strength ?
It has to do with the voids in a casting, forged aluminium has no voids and is much stronger than cast. Here is just one of many articles on the subject...
http://www.azom.com/article.aspx?ArticleID=1510 http://sheldonbrown.com/dp-forging.html"The strongest result is usually from forging. As metal cools, it forms "grains". The grains are strong, but they don't "stick" to each other perfectly. So castings may well break, and if you look at the break, it will show a bumpy "matte" surface, as it will have separated between individual grains. In metalurgists terms, it shows poor ductility."
BTW a bash plate is there to protect the cast alloy parts of a bike engine.

You also need to fit it far enough from the castings you need to protect to give the bash plate room to bend and absorb impacts without touching the engine parts in the process.