A fuel pretreater apparatus for pretreating fuel for combustion is provided. A conversion tube is provided for vaporized fuel to flow therethrough. The conversion tube includes an intake end for receiving the vaporized fuel and an outlet end for dispersing the vaporized fuel. The conversion tube includes a hollow tapered interior wall having a narrower diameter near the intake end and a wider diameter near the outlet end. A tapered conversion rod is removably placed inside the conversion tube. The tapered conversion rod is conically tapered along at least one half of a length of the tapered conversion rod. The tapered conversion rod includes a narrow end corresponding to the narrower diameter of the conversion tube near the intake end and a wide end corresponding to the wider diameter of the conversion tube near the outlet end.