You may need to weld motorcycle gas tanks when fabricating a custom tank or repairing damages. Typical welding points include the mounting hubs and the collar that fits over the upper tube of the motorcycle frame. Two-piece gas tanks have seams that can rust or separate over time and require welding. Gasoline fumes are extremely volatile; take precautions before welding a previously used motorcycle gas tank. Prepare for the welding job with the tank completely empty and removed from the motorcycle.
Close the fuel petcock on the tank, and remove the gas cap. Fill the gas tank with soapy water, and vigorously slosh the water inside the tank. Empty the soapy water into a 5-gallon bucket for proper disposal later. Open the fuel petcock.
Rinse the inside of the tank thoroughly with fresh water. Wet one finger under the rinsing water as you empty the water into the bucket. Any hint of gasoline odour means you must wash and rinse the tank again. Clean and rinse the tank again if necessary, and allow it to remain in a ventilated area until the inside is completely dry.
Remove any metal burrs from the area of repair using a flat file. If necessary, turn the tank over and use a welder's chipping hammer to tap debris out of a seam. Use a welder's chipping hammer to round the edges of a seam, then file that area of the seam.
Sand the area to be welded to bare metal using a sanding block and heavy garnet sandpaper. Residual paint and rust will affect the integrity of the weld; sand thoroughly.
Position the tank on a workbench for welding. Apply heat to the area of the weld to burn away any residual debris from the preparation procedure. Weld the tank by making a continuous weld that overlaps the adjacent undamaged welds.
Allow the welds to cool completely. File the welds if necessary for a consistent appearance. Touch up the weld with the sanding block and garnet sandpaper.
Ask an experienced welder to oversee the welding.
Wear the proper safety goggles and gloves when welding.