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Harley-Davidson Softail Fat Boy: Detailed Specs, Background, Performance, and More

Harley-Davidson Softail Fat Boy: Detailed Specs, Background, Performance, and More

Harley-Davidson has always been surprising to the outer world, whether in the name of making extraordinary motorcycles or providing long-lasting, high-quality, and super cool machines.


The journey of the Softail Fatboy, which is one of the most iconic and best-selling Harley-Davidson models, started in 1989. It can be easily guessed that the company wanted to rock the Daytona Bike Week with a prototype custom-look bike with a pumped-up Softail with solid wheels, wide bars, a shotgun exhaust, and finished in matte grey.

In 1990, Harley-Davidson witnessed a huge demand for its chasing Softail Fatboy by motorcycle enthusiasts. When, in 1991, the H-D Fatboy made a starring appearance alongside Arnold Schwarzenegger in the highly popular ‘Terminator sequel, the bad boy status of this now iconic bike was assured.


Later on, Harley-Davidson made a lot more improvements and major changes to its Softail line. Putting the traditional old and less powerful engines aside, the bigger Milwaukee-Eight engines (107 and 114) are installed on the two new lightweight and very stiff frames.


Through a period of more than 30 years and having only received one major update, the Harley-Davidson FLSTF Custom Fatboy still turns heads and delivers the kind of attitude that only American heavy metal can. But is it all show and no go?

In this article, we’ll be discussing the detailed specs, background, performance, and more of the Harley Custom Fatboy FLSTF.

1. A Brief History of the Harley-Davidson Softail Fatboy

The Harley Softail Fatboy is a V-Twin cruiser motorcycle with solid-cast disc wheels. It was primarily designed by Willie G. Davidson and Louie Netz for the Daytona Bike Week rally at Daytona Beach in 1988 and 1989. Softail Fat Boys were produced from 1990 to 2017 under the name coded FLSTF and FLFB (and FLFBS) from 2018.


Like some of the other Harley-Davidson models, the Fatboy is also affiliated with a controversial story regarding its name. A huge number of the audience think Harley-Davidson named this bike after the B-29 Bomber called "Fat Boy," dropped on Japan during WWII as a symbolic insult to Japanese motorcycles.


Although it was completely a false myth, Harley-Davidson had nothing to do with this false etymology claim. In a 2015 interview, Scott Miller (Harley’s Vice President of Styling and Product Development) cleared the accusations that the name was simply descriptive and had nothing to do with Harley’s Japanese competitors.


The Fat Boy's frame was based on the 1984 "Softail," which seems to have a rigid hardtail chassis but actually has a swinging arm with concealed springs, which was built in a Missouri garage in the 1970s by a mechanical engineer named Bill Davis and later patented in 1976.


Willie G, the grandson of Harley-Davidson co-founder William A. Davidson, initially declined engineer Bill Davis' Softail proposal; but, the business later relented, purchasing the rights and constructing its own Softail frame in-house.

  • After 1994, the seamless exhaust was introduced.
  • In 1996 Fat Boy, the master cylinder, and switchgear were revised.
  • In 1999 Fat Boy, a new 88 cu in (1,450cc) Twin Cam engine for the 2000 model year was used. This necessitated a bespoke engine variant and changes to the frame.
  • In 1999 Fat Boy, a new 88 cu in (1,450cc) Twin Cam engine for the 2000 model year was used. This necessitated a bespoke engine variant and changes to the frame.
  • In 2002 Fat Boy, bullet-style indicators, immobilizer, and alarm were added.
  • In 2005 Fat Boy, a 15th Anniversary version was sold with a “Screamin’ Eagle” engine, custom wheels, and special paint.
  • In 2007 Fat Boy, the displacement was increased to 1,584cc (97.7 cu in) and the transmission upgraded to six speeds.
  • In 2010 Fat Boy, FLSTFB (Fat Boy Lo) had the lowest ever seat height.>
  • In the 2012 Fat Boy, the displacement increased to 1,690cc (103 cu in) Twin Cam engine with the rest of the Softail range.

The base machine for 2005 was powered by a 1449cc fuel-injected engine and offered in 13 color schemes. A limited-edition 15th Anniversary FLSTF model with the huge bore 1550cc lump and a slew of accessories including paint, seat, and chromed solid wheels was available for another grand.


From the tenure of 1994 to 2018, there have been countable changes in the Softail series. The major change made by the company was the replacement of Twin Cam (1450 cc) engines with new twin-counterbalanced Milwaukee-Eight engines, along with the Showa front and rear suspension.


From 2018 onwards, the Harley Custom Fatboy comprises two variants:

  • The FLFB 107 cu in (1,746cc) with 109 lb-ft (148 Nm), and
  • The FLFBS 114 cu in (1,868cc) with 119 lb-ft (161 Nm)

Later in 2018, the Showa rear monoshock suspension was mounted behind the seat, which was earlier replaced with twin shocks for better riding experience and balancing. Moreover, to provide a controlled ride with improved handling and more comfort, the front forks contain a Showa “Dual Bending Valve” (SDBV).


Except for the changes in engine specifications and shocks for a better riding experience, Harley-Davidson lightened the chassis more than the earlier Softail and Dyna series. Further upgrades include 18-inch “Lakester” rims, with wider 160mm front and 240mm rear tires, and an LED headlight.

From 2020 onwards, the Fat Boy is only available with the Milwaukee-Eight 114 engine.

2. Harley-Davidson Softail Fatboy at First Glance

This is the bike that can provide you with that surprising and desired neck-turning ovation you want while riding across the streets. Although it is pure fun, riding this bike and its bulky, big look feels really good and enhances your swag.


Unlike the other Harley-Davidson Dyna and Sportster variants, the Softail is a lot more. There are many basic yet significant changes that distinguish Fat Boy from any other H-D model.


First of all, you’ll notice a big 18.9-liter fuel tank that allows you to ride some extra miles on scenic motorcycle roads and highways. You can rely on it if you are going on a motorcycle camping trip and traveling from one state to another.


In front, you’ll find an eye-catching headlight covered with a metallic guard attached to the shocks. The handlebar is wide, but the height and length provide an easy reach and help the rider maintain a good riding posture on long motorcycle trips.

The main feature that differentiates the Softail Fat Boy from the other H-D models is its Lakester rims. These babies play a crucial role in providing the Fat Boy with more of a muscular look.


The seat height is perfect and easily reachable, and the cushioning at the back increases the comfortability level of the rider. As well as that, the footrests are positioned at such a perfect angle that the rider doesn’t feel any tiredness in their legs on longer journeys. From the rear, the bike’s looks are all business.


That rear tire provides much-needed traction to get the bike off the line without even a hint of wheel spin. And this is where a bike like this really shines. The Softail Fat Boy is not a high revving superbike kind of motorcycle designed to perform well over 200 km/h. It is rather a stylish cruiser, with more than enough get-up and goes to make the experience memorable. Given that the highest torque number hits at 3000rpm, by 2000rpm, this V-twin is likely producing more torque than many modern superbikes have at their high-revving peak, thanks to the 1,868cc engine.


From a cold start, unless the Fat Boy is performing a 7000+ rpm launch, the superbike will simply release the clutch, roll onto the throttle, hit that mountain of torque, and arrive at 60km/h well before the other riders are in their stride.


Conclusively, the Harley-Davidson Custom Fat Boy is comfortable and easy to ride, doesn’t make things difficult with its operation, and provides a pure riding experience that stays with you long after you’ve jumped off.

3. Harley-Davidson Softail Fatboy: Buyer’s Guide

3.1. I’m 5’4. Shall I Go for Harley Fat Boy or Not?

Well, the best way to find a bike suitable for your height is to go to the showroom and take a test ride. Make sure while taking a test ride that you sit with good riding posture, your hands are straight, and you can easily reach the handlebars.


If you're 5'4", you can definitely go for the Harley Softail Fat Boy because it's only 4.5 inches off the ground, so mounting won't be a problem. However, there is one aspect on which you should concentrate: the inseam. Research can only be done by visiting a showroom where you intend to buy, not on the internet. It's impossible to tell if you're flatfooted on the ground astride the bike unless you sit on it. When you're on the bike, try backing it up while seated. This will give you some assurance that the bike will fit you properly.


Another way to try out different models is to rent a motorcycle. By doing that, you will get a wide exposure to different motorcycles and find the best suitable option for yourself easily.

3.2. What is the Difference Between a Softail and a Fatboy?

The most significant difference between the standard Softail and the Softail Fatboy is that one has standard parts on the Softail frame and the other has fatter parts on a Softail frame, which differentiates the Fat Boy from the standard Softail and also makes the H-D Fat Boy slightly heavier.


If you are a beginner, read these Motorcycle 101 Guides to get to know everything about motorcycle riding.

3.3. What Makes a Harley Softail a Fat Boy?

The Softail chassis comes in a variety of models, including the Fatboy. It is distinguished by a huge fuel tank and solid or slightly perforated holes around the disc wheel's outside edge. It became famous when Arnold Schwarzenegger rode this bike in his movie “Terminator” in 1991.

4. Harley-Davidson Softail Fatboy: Detailed Specs

4.1. Dimensions

Length 93.3 in.
Ground Clearance 4.5 in.
Seat Height, Laden 25.9 in.
Rake 30
Trail 4.1 in.
Wheelbase 65.6 in.
Front Tire Specification 160/60R18,70V, BW
Rear Tire Specification 240/140R18,79V, BW
Tire, Type Michelin Scorcher “11” front and rear
Oil Capacity (W/Filter) 5 qt.
Fuel Capacity 5 gal.
Weight, As Shipped 671 lb.
Weight, In Running Order 699 lb.

4.2. Engine

Engine Milwaukee-Eight 114
Bore 4.016 in.
Displacement 114 cu in
Stroke 4.5 in.
Compression Ratio 10.5:1
Exhaust 2-into-2 staggered; catalyst in muffler
Fuel System Electronic Sequential Port Fuel Injection (ESPFI)

4.3. Performance

Engine Torque 119 ft-lb
Engine Torque (RPM) 3000
Engine Torque Testing Method J1349
Lean Angle, Right (DEG.) 25.6
Lean Angle, Left (DEG.) 25.6
Fuel Economy 47 mpg
Fuel Economy Testing Method Estimated City/Hwy

4.4. Drive Train

Primary Drive Chain, 34/46 ratio
Gear Ratios (Overall) 1st 9.311
Gear Ratios (Overall) 2st 6.454
Gear Ratios (Overall) 3st 4.793
Gear Ratios (Overall) 4st 3.882
Gear Ratios (Overall) 5st 3.307
Gear Ratios (Overall) 6st 2.79

4.5. Chassis

Front Fork Dual-Bending Valve 49 mm telescopic with aluminum fork triple clamps; dual-rate spring; “beer can” covers
Rear Shocks Hidden, free piston, coil-over monoshock; 43mm stroke; toolless hydraulic preload adjustment
Wheels, Front Type Machined, Lakestar cast aluminum
Wheels, Rear Type Machined, Lakestar cast aluminum
Brakes, Type Front and rear silver, Split 7-spoke floating rotors
Brakes, Caliper Type 4-piston fixed front and 2-piston floating rear

4.6. Electric

Gauges 5-inch analog speedometer with digital gear, odometer, fuel level, clock, trip, range, and tachometer indication
Lights (As Per Country Regulation), Headlamp, Tail/Stop/Front Signal Lights All LED headlamps, low and high beam with signature position lighting, All LED tail/stop lamps with signature tail lighting, LED Bullet Turn Signals

5. Aftermarket Luggage and Modification Options for Harley Softail Fatboy

One thing that every rider does after buying a Harley-Davidson motorcycle is to give his or her bike some extra touch-ups. Although Harley-Davidson makes perfect bikes, riders do so to make their bike unique and different-looking from every other Harley out there.


Aftermarket luggage and modifications make this dream possible. There are many vendors ready to make your Harley Softail Fat Boy a custom and modified look by providing motorcycle bags like saddlebags and aftermarket parts like sissy bars and motorcycle seats.


Before getting your hands into something overpriced, rethink the moral lesson that things are not always what they seem, before making any choices. Rather, you can get the best quality motorcycle luggage bags at cheap prices. Some vendors like Viking Bags provide premium quality motorcycle panniers at a cheap rate without compromising the quality.

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