It is neither difficult nor expensive to replace your old gas tank. Here is a fuel tank for the Baja 50cc ATVs such as the BA50 and Baja 50 (WD50).
As well as the Baja models, this black plastic gas tank fits numerous Chinese ATVs or quads in the 50cc range. In addition, this handy gas tank can be adapted to a wide variety of applications, garage and custom builds.