Motorcycle Bungs

THREADED MOTORCYCLE BUNGS FOR CUSTOM FABRICATION

Making a bung one-off on a lathe takes time, and if your time is worth more than the cost of a pre-made part, the math is simple. Every bung in this collection is made by Lowbrow Customs in Ohio from 1018 cold rolled steel or 6061 aluminum. The range covers every common weld-in thread point used on motorcycle, chopper, and hot rod builds: coped bungs for round tubing, tophat blind bungs for flat surfaces, counterbore bungs for flush bolt heads, NPT pipe thread bungs for fittings and sensors, petcock bungs for gas tanks, and riser bungs for custom handlebar trees. Packs of 2 and 4, plus assortments for shops and active builders.

STEEL BUNG PROFILES

Bung profile determines where and how the bung welds in. Choose based on the surface it is going into:

• Coped Bungs: Machined with a saddle cut on the base that matches round tubing. The coped profile seats flush against the tube wall so the weld closes fully without gaps. Available in 5/16-18 and 3/8-16 thread in multiple lengths from 1/2 inch to 1-1/2 inches. The go-to bung for any mount welding directly onto a frame tube, oil tank rail, or sissy bar upright.

• Tophat Blind Bungs: Flanged bungs for flat surfaces and sheet metal where a standard threaded cylinder would pull through. The flange bears the load instead of relying purely on the weld. Available in 5/16-18, 3/8-16, and 1/4-20 thread in steel, and 5/16-18 and 3/8-16 in aluminum.

• Counterbore Bungs: Machined so the bolt head sits recessed flush inside the bung, producing a flat surface after fastening. Available for 5/16 and 3/8 Allen head bolts. Useful anywhere a protruding bolt head creates a clearance problem or a clean flush surface is part of the build direction.

• Full Radius Bungs: Rounded outer profile for tube applications where the smooth exterior matters. Available in 3/8-16 thread in steel.

• Straight Threaded Bungs: Standard cylinder profile in 5/16-18 and 3/8-16 thread, 1 inch and 1-1/2 inch lengths. The universal bung for flat plate and sheet metal weld-ins.

PETCOCK AND SPECIALTY BUNGS

Specific thread forms for fuel, oil, and handlebar applications:

• 22mm Petcock Bungs: The correct thread size for Harley-Davidson petcocks and most aftermarket fuel valves. Available in standard and long Frisco-style versions. The Frisco variant extends the bung to raise the petcock position for Frisco-mounted tanks where the standard length sits too low. Among the most-used bungs in the collection.

• NPT Petcock Bungs: 3/8 inch NPT and 1/4 inch NPT petcock bungs in steel and aluminum for tanks running NPT-thread petcocks. The 3/8 NPT version also comes in a long Frisco style.

• 1/8 inch NPT Tophat Bungs: For breather fittings, oil line fittings, pressure sender ports, and any application using 1/8 inch NPT hardware. Available in both steel and aluminum.

• Riser Bungs: 1/2-13 threaded steel riser bungs for welding handlebar riser mounting points into custom top clamps and triple trees. Saves the machining step on any custom tree build.

• Filler Cap Bungs: Weld-in steel bung for 1-5/16 inch filler caps, for custom oil and gas tank builds where a clean filler cap seat is needed.

• Triumph Oil Feed Bung: OEM-spec threaded steel bung for Triumph oil feed applications on vintage British builds.

Browse motorcycle oil tank hardware and motorcycle gas tanks for petcock and filler cap hardware alongside the bung collection. For tabs and mounting plates, see motorcycle frame fabrication parts.