My doodles.

  I did these drawings just to give me a better idea of what was getting messed up in my head. They are from the point of view of the PL (Parting Line) of the way the tank will sit in the cope and drag, not on a bike. I was just trying to figure what the half of the core would look like, but until I drew them I didnt realize that the rear mounting point would extend above the drag into the cope. This realization changed what I thought would be a simple pattern into a more complex one. I'll explain in detail about why this is more complex when I actually make the pattern and post pix of how to set them in sand. Always better to figure things out on paper b4 cutting into expensive materials trying to make a pattern.