A chopper, even a plastic model, needs a custom fuel tank. Here is how to build one.
I have based my fuel tank design on the original WL750 fuel tank, but made it slimmer and slightly shorter and flatter. The easiest way to do this is to make a positive mold from the original tank and use that for vacuum thermoforming. So the first step is to fill both halves of the original fuel tank with modeling clay. The left half can be seen in the picture.
These are the halves after letting them dry. Of course there are lots of gaps and extra material that oozed out of the part when squeezing the clay in, so the next step is to remove the extra stuff with a milling drill and fill the gaps with body putty.
These are the molds after several iterations of filling, filing, and sanding. They still have the width of half the original WL750 fuel tank, but this will change in the next step, which is vacuum thermoforming. You can read about it in the description of a different model. By partially burying the molds in the granulate in the vacuum chamber, the resulting shape will become slimmer.
Here are the thermoformed parts before extracting them from the polystyrene sheet that the thermoforming device processes.
The next step is to remove the parts from the sheet with a milling drill. Unfortunately the PS sheet warped after thermoforming, most probably because it was too cold in the room and it cooled down too quickly. This may cause some trouble below.
Fitting test. Not good. After gluing the halves together, some more filling and filing will be required. What you see in the picture is the top side of the fuel tank. There is a gap for attaching it to the frame on the bottom.
The fuel tank after a lot of filling, sanding, and polishing.
Fitting test. Very nice!
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