These petcocks for older Yamaha YZ models are a great mod for the Full Floater RM models! They offer the higher flow of the larger 1/4″ diameter fuel line. For carbs with smaller fuel inlets like the stock RM carbs, you leave a small piece of the smaller fuel line and slip the bigger line over it. This mod is discussed in detail in this article: Motocross Action Magazine – RM Carb Mods – May 1983
