You have to remove anything from the vicinity of the weld that might be damaged by heat, or might catch fire. The ride-on frame will be mild steel or low-alloy steel, so it is easy to gas weld with ordinary mild steel filler rods. To arc weld you need to ensure the electrode size, material, voltage and welding current are suitable. For any type of welding you need to remove paint and rust first.
If you follow correct practice, you can weld to the frame.
