Screw Top Fat Bob 5 Gallon Gas Tank For Harley 1936-1985

Vintage Soul Meets Modern Convenience: The 5 Gallon Screw Top Fat Bob Tank

For owners of classic Harley-Davidson Big Twins, the balance between historical accuracy and modern rideability is always a priority. The Screw Top Fat Bob 5 Gallon Gas Tank is the perfect solution for those who want to maintain the legendary silhouette of the 1936–1984 era while benefiting from a massive fuel capacity and modernized hardware. Whether you are piloting a Knucklehead, Panhead, or Shovelhead, these tanks offer the muscular “Fat Bob” stance that has defined American touring for nearly half a century. By increasing your capacity to a full five gallons, you transform your vintage machine into a capable long-distance cruiser, ready to tackle state lines with fewer interruptions.

Engineered for Classic Big Twin Frames

These tanks are specifically designed to fit the 4-speed Big Twin frames utilized from 1936 through 1984. They are compatible with a wide range of models, including the FL, FLH, and FX series. The split-tank design is faithful to the original Fat Bob aesthetic, mounting securely to your frame’s seat post and front tank mounts. One of the most significant upgrades in this set is the transition to screw-in style gas caps. While original vintage tanks often used bayonet or cam-lock caps which were prone to leaking or “popping,” these tanks are threaded to accept 1983-up style caps, providing a much more reliable, pressurized, and leak-free seal—essential for protecting your custom paint job.

Premium Construction and Technical Specs

V-Twin builds demand high-quality materials to withstand the heavy pulses of a large-displacement engine. These tanks are constructed from heavy-gauge, deep-drawn steel with precision welds to ensure they can handle the vibrations of a rigid or rubber-mounted Big Twin.

• Total Capacity: 5.0 Gallons (approx. 18.9 liters).
• Petcock Compatibility: Threaded for a standard 22mm external thread petcock on the left side.
• Cap Design: Dual screw-in bungs for modern, vented gas caps.
• Instrument Integration: Designed to accept standard 2-light or 3-light Fat Bob dash assemblies and speedometers.

Custom Preparation and Painting Excellence

This tank set arrives in a raw, unfinished steel state. This is the preferred choice for custom builders, as it allows for perfect metal finishing and a custom paint scheme that matches your vision perfectly. Because these tanks are intended for classic builds, they provide a massive canvas for traditional pinstriping, gold leafing, or classic two-tone Harley colors. To ensure a professional result, we strongly recommend that these tanks be pressure tested and internally sealed with a high-quality tank liner before painting. This step is critical to protect the raw steel from the corrosive effects of modern ethanol-blended fuels and to prevent any future damage to your expensive custom finish.

Why Choose the Screw Top Fat Bob Upgrade?

Upgrading to these 5-gallon tanks is more than just a cosmetic change; it’s a commitment to the road. By choosing the Screw Top Fat Bob Tanks, you are respecting the heritage of your 1936–1984 Harley-Davidson while making it a more practical, reliable, and long-legged machine. No more hunting for gas stations every 80 miles. Experience the freedom of the open road with the confidence of a 5-gallon reservoir and the timeless style of a classic Fat Bob. Whether you are restoring a 1948 Panhead or customizing a late-era Shovelhead, these tanks are built to lead the way for decades to come.