The 2012–2017 Harley-Davidson Dyna Twin Cam 103 (FXDF Fat Bob) is a factory custom cruiser motorcycle that represents the final evolution of the celebrated Dyna platform before its integration into the Softail line. Characterized by its aggressive, muscular stance and the significant power upgrade of the Twin Cam 103 engine, this era of the Fat Bob solidified its position as a performance-oriented cruiser within the Harley-Davidson lineup. It appealed to riders seeking a blend of traditional Harley character with modern power and a commanding road presence.
The introduction of the 2012 model year marked a pivotal update for the Dyna family, most notably the transition from the previous Twin Cam 96 engine to the larger Twin Cam 103. This change increased displacement from 96 cubic inches (1584cc) to 103 cubic inches (1690cc). The primary difference felt by the rider was a substantial boost in low-end torque, resulting in stronger acceleration from a standstill and more responsive roll-on power for highway passing. While horsepower gains were modest, the increased torque aligned perfectly with the cruiser ethos of effortless, V-twin muscle. Aesthetically, the motorcycle received subtle refinements, including a new tail light assembly and blacked-out detailing on the engine and triple clamps, further enhancing its aggressive, custom-inspired look.
Key Features of the Harley-Davidson Dyna Twin Cam 103 Fat Bob
The Fat Bob’s design and engineering during this period were focused on delivering a unique riding experience defined by power, style, and a direct connection to the road.
Powertrain and Performance
At the heart of the FXDF Fat Bob was the air-cooled Twin Cam 103 V-twin engine. This rubber-mounted powerplant was engineered to deliver a peak torque of approximately 99 ft-lb, providing the signature Harley-Davidson rumble and strong, accessible performance across the RPM range. The engine was paired with a 6-speed Cruise Drive transmission, which offered smooth shifting and a tall final gear for relaxed highway cruising. The power was delivered to the rear wheel via a clean and low-maintenance belt drive system. The distinctive “Tommy Gun” 2-1-2 collector exhaust with dual mufflers not only contributed to the bike’s stout appearance but also produced a deep, satisfying exhaust note.
Styling and Ergonomics
The Fat Bob’s styling is arguably its most defining feature. It projected a bulldog-like stance, anchored by its namesake thick tires mounted on 16-inch black, slotted-disc cast aluminum wheels. The front end was dominated by an unmistakable dual bullet headlamp assembly, a signature element that set it apart from other models. Further contributing to its aggressive look were the drag-style handlebars on a blacked-out riser, forward-mounted foot controls, and a sleek, bobbed rear fender with a minimalist dual-ring LED tail light. The two-up seat was designed to be both stylish and reasonably comfortable for the rider on moderate journeys.
Chassis and Handling
The Fat Bob was built on Harley-Davidson’s robust Dyna frame, which was known for its strength and classic lines featuring exposed dual coil-over rear shock absorbers. This setup provided a more traditional look and feel compared to the hidden-shock Softail design. The rubber-mounted engine effectively isolated the rider from excessive vibration at idle and cruising speeds, enhancing comfort. While its heavy curb weight and raked-out front end made it exceptionally stable on straightaways, it required deliberate rider input to navigate tight corners. The braking system featured dual disc brakes at the front, providing confident stopping power for a motorcycle of its size and weight. Anti-lock Braking System (ABS) became a standard feature in later years of this production run, further improving safety.
Specifications
<table>
<tr><td colspan=”2″><b>General</b></td></tr>
<tr><td>Brand</td><td>Harley-Davidson</td></tr>
<tr><td>Model</td><td>Dyna Fat Bob</td></tr>
<tr><td>Model Class</td><td>FXDF</td></tr>
<tr><td>Model Years</td><td>2012–2017</td></tr>
<tr><td>Type</td><td>Cruiser</td></tr>
<tr><td>Maximum passengers</td><td>2</td></tr>
<tr><td colspan=”2″><b>Performance</b></td></tr>
<tr><td>Max. power</td><td>~80 Hp (estimated)</td></tr>
<tr><td>Max. torque</td><td>98.8 ft-lb (134 N•m) / 3500 RPM</td></tr>
<tr><td>Top designed speed</td><td>~110 mph (177 km/h)</td></tr>
<tr><td colspan=”2″><b>Size</b></td></tr>
<tr><td>Length</td><td>94.5 in. (2400 mm)</td></tr>
<tr><td>Width</td><td>35 in. (889 mm)</td></tr>
<tr><td>Wheelbase</td><td>63.7 in. (1618 mm)</td></tr>
<tr><td>Seat height (laden)</td><td>26.1 in. (663 mm)</td></tr>
<tr><td>Ground clearance</td><td>4.9 in. (125 mm)</td></tr>
<tr><td>Curb weight (in running order)</td><td>706 lb. (320 kg)</td></tr>
<tr><td colspan=”2″><b>Engine</b></td></tr>
<tr><td>Type</td><td>Air-cooled, Twin Cam 103™, 45° V-Twin</td></tr>
<tr><td>Displacement</td><td>103.1 cu in (1690 cc)</td></tr>
<tr><td>Bore × Stroke</td><td>3.87 in. × 4.37 in. (98.4 mm × 111.1 mm)</td></tr>
<tr><td>Compression ratio</td><td>9.6:1</td></tr>
<tr><td>Fuel supplying system</td><td>Electronic Sequential Port Fuel Injection (ESPFI)</td></tr>
<tr><td>Lubricating system</td><td>Dry sump</td></tr>
<tr><td>Oil capacity</td><td>3 qt (2.8 L)</td></tr>
<tr><td colspan=”2″><b>Transmission</b></td></tr>
<tr><td>Transmission type</td><td>6-speed Cruise Drive®</td></tr>
<tr><td>Clutch type</td><td>Multi-plate, wet</td></tr>
<tr><td>Primary Drive</td><td>Chain, 34/46 ratio</td></tr>
<tr><td>Final Drive</td><td>Belt, 32/66 ratio</td></tr>
<tr><td colspan=”2″><b>Chassis</b></td></tr>
<tr><td>Frame</td><td>Mild steel, tubular frame; rectangular section backbone</td></tr>
<tr><td>Front Tire</td><td>130/90B16 67H</td></tr>
<tr><td>Rear Tire</td><td>180/70B16 77H</td></tr>
<tr><td>Wheels</td><td>Black, Slotted Disc Cast Aluminum</td></tr>
<tr><td>Brakes</td><td>Front: Dual 4-piston fixed caliper; Rear: 2-piston torque-free floating caliper</td></tr>
<tr><td>Rake (steering head)</td><td>29°</td></tr>
<tr><td>Trail</td><td>4.92 in. (125 mm)</td></tr>
<tr><td>Capacity of fuel tank</td><td>5.0 gal (18.9 L)</td></tr>
<tr><td>Fuel consumption (Combined)</td><td>~42 mpg (5.6 L / 100 km)</td></tr>
<tr><td colspan=”2″><b>Suspension</b></td></tr>
<tr><td>Front Suspension</td><td>49 mm telescopic fork</td></tr>
<tr><td>Rear Suspension</td><td>Dual coil-over shocks, preload adjustable</td></tr>
</table>
