Harley History


1901 William S. Harley, age 21, completes a blueprint drawing of an engine designed to fit into a bicycle.    
1903 21-year old William S. Harley and 20-year old Arthur Davidson make available to the public the first production Harley-Davidson® motorcycle. The bike was built to be a racer, with a 3-1/8 inch bore and 3-1/2 inch stroke. The factory in which they worked was a 10 x 15-foot wooden shed with the words "Harley-Davidson Motor Company" crudely scrawled on the door. Arthur's brother Walter quits his job in Kansas and joins their efforts on April 17th.  

Henry Meyer of Milwaukee, a schoolyard pal of William S. Harley and Arthur Davidson, buys one of the 1903 models directly from the founders.    
The first Harley-Davidson Dealer, C.H. Lang of Chicago, Ill., opens for business and sells one of the first three production Harley-Davidson motorcycles ever made    
1905 On July 4th, a H-D motorcycle wins a 15 mile race in Chicago with a time of 19:02. In Milwaukee, the first full-time employee is hired.    
1906 A new factory, measuring 28 x 80 feet, is built on the Chestnut St. site, later renamed Juneau Avenue. Staff size is increased to six full-time employees. Also, the first motorcycle catalog is produced by the Company and the nickname "Silent Gray Fellow" is used for the first time.    
1907 In 1907, four trophies were awarded for winning races on Harley-Davidson® motorcycles. They were: Speed Test Milwaukee Hillclimb, 30 May 1907, won by Walter Davidson; Motorcycle Flying Start, Milwaukee, 27 July 1907, won by the Harley-Davidson Motor Company; Five Mile Handicap, Janesville, Wisconsin, won by Arthur Davidson; Special Handicap Derby Day Races, Milwaukee, 27 July 1907, won by the Harley-Davidson Motor Company.    
William A. Davidson, brother to Arthur and Walter Davidson, quits his job as tool foreman for the Milwaukee Road railroad and joins the Motor Company.    
Harley-Davidson Motor Company is incorporated on September 17th. The stock is split four ways between the four founders, and staff size has more than doubled from the previous year to eighteen employees. Factory size is doubled as well. Dealer recruitment begins, targeting the New England region.    
1908 Walter Davidson scores a perfect 1,000 points at the 7th Annual Federation of American Motorcyclists Endurance and Reliability Contest. Three days after the contest, Walter sets the FAM economy record at 188.234 miles per gallon. Word of Harley-Davidson's extremely tough motorcycle spreads rapidly.    
The first motorcycle sold for police duty is delivered to the Detroit, Mich., police dept.    
1909 The six-year-old Harley-Davidson Motor Company introduces its first V-twin powered motorcycle. With a displacement of 49.5 cubic inches, the bike produces seven horsepower. The image of two cylinders in a 45-degree configuration would fast become one of the most enduring icons of Harley-Davidson history. Also available for the first time from the Motor Company are spare parts for motorcycles.    
1910 The famed "Bar & Shield" logo is used for the first time. It is trademarked at the U.S. Patent office one year later.    
At least seven different first place finishes are captured at races, endurance contests and hillclimbs across America. All seven winners are riding Harley-Davidson® motorcycles.    
1911 The "F-head" engine becomes a workhorse of the Harley-Davidson motorcycle until 1929.    
1912 Construction begins on what will become the six story headquarters and main factory building at Juneau Ave. in Milwaukee. A separate Parts and Accessories Department is formed.    
H-D exports motorcycles to Japan, marking the first ever sales outside of the U.S. Dealer network grows to over 200 nationwide.    
1913 The Racing Department is formed, with William Ottaway as its first Assistant Engineer to racing engineer William S. Harley. Also, the Package Truck commercial delivery van is offered for the first time.    
1914 Sidecars are made available to Harley-Davidson buyers. Clutch and brake pedals now available on F-head singles and twins.    
The Motor Company formally enters motorcycle racing this year. The first Racing Engineer is William S. Harley. Within a few short years, team Harley-Davidson is referred to informally as the "Wrecking Crew" because of their incredible dominance of the sport.    
The Two-Speed rear hub transmission is introduced for one year only in the Model 10F. Patented by William S. Harley, it was effective but discontinued in order to further improve drivetrain function in 1915 with a three-speed design.    
1915 Harley-Davidson motorcycles are now available with three speed sliding-gear transmissions with final and primary drive on the same side.    
1916 The Enthusiast begins its reign as the longest continuously published motorcycle magazine in the world.    
The Eight-Valve Racer introduced (1916-1928). In the 1921 racing season alone, Harley-Davidson’s Racing Team won every single national championship race relying heavily upon the Eight-Valve.    
1917 During this year, roughly one-third of all Harley-Davidson motorcycles produced are sold to the U.S. military. The Quartermasters School, a department of Harley-Davidson devoted to training military mechanics on Harley-Davidson motorcycles, opens for business in July. It will later become the Service School.    
The sale of Harley-Davidson bicycles begins. Individual components are made by the Davis Sewing Machine Co. of Dayton, Ohio. The bicycles are sold through the H-D dealer network.    
1918 Almost half of all Harley-Davidson motorcycles produced are sold for use by the U.S. military in World War I. At War's end, it is estimated that the Army used some 20,000 motorcycles in their efforts, most of which were Harley-Davidsons. One day after the signing of the Armistice, Corporal Roy Holtz of Chippewa Falls, Wis., is the first American to enter Germany. He is riding a Harley-Davidson.    
1919 The 37 cubic inch opposed twin cylinder Sport model is introduced and gains great popularity overseas. Unique not only for the cylinder configuration, which was directly opposed and flat, the Sport quickly earns a reputation for being uncommonly quiet.    
1920 By 1920, Harley-Davidson is the largest motorcycle manufacturer in the world. New Harley-Davidson® motorcycles can be purchased from over 2,000 dealers in 67 countries worldwide.    
Leslie "Red" Parkhurst breaks 23 speed records on a Harley-Davidson 61 cubic inch racing motorcycle. Also, the "hog" association starts when the racing team's mascot, a pig, is carried on a victory lap after each race won by the team.    
1921 The first 74 cubic inch V-twin engine is introduced on the JD and FD models. Harley-Davidson dealerships are now found in sixty-seven countries.    
Harley-Davidson riders sweep all eight National Championship races.    
1925 Gas tanks on all models now have a distinct teardrop shape. This basic appearance is set for all subsequent Harley-Davidson motorcycles.    
Joe Petrali begins racing for Harley-Davidson. He would become one of the most successful dirt-track racers for Harley-Davidson, and one of the most successful racers of all time.    
1926 Single-cylinder motorcycles are again sold by Harley-Davidson for the first time since 1918. Models A, AA, B, and BA are available in side-valve and overhead-valve engine configurations.    
1928 The first Harley-Davidson two cam engine is made available to the public on the JD series motorcycles. The bike is capable of top speeds between 85 - 100 mph.    
Front wheel brakes are now available on all Harley-Davidson motorcycles.    
1929 The 45 cubic inch V-twin engine (later to be known as the "flathead") is introduced on the D model. The engine proves to be so reliable that variations of it are available on Harley-Davidson motorcycles as late as 1972.    
1930 Bill Davidson, Jr. wins the Jack Pine endurance contest with 997 points of 1,000. All individual class winners are riding Harley-Davidson® motorcycles.    
1931 All of Harley-Davidson's remaining American competition is now gone except Indian (Hendee Manufacturing). Indian and Harley-Davidson are the only two American motorcycle manufacturers until 1953.    
1932 The 45 cubic inch-driven, three-wheeled Servi-car begins its 41 year run as a popular commercial and police vehicle.    
In dirt track racing, Harley-Davidson racer Joe Petrali begins a five-year consecutive streak of winning the AMA Grand National Championship. Petrali also wins the National Hill-Climb Championships for 1932 to 1935.    
1933 An art-deco "eagle" design is painted on all gas tanks. This marks the beginning of graphic designs on Harley-Davidson motorcycles (with the exception of previously special order-only paint schemes). This styling decision was made in part to stimulate the low sales numbers caused by the Great Depression.    
1935 The Japanese motorcycle industry is founded as a result of Harley-Davidson licensing blueprints, tools, dies and machinery to the Sankyo Company of Japan. The result is the Rikuo motorcycle.    
Joe Petrali and his Harley-Davidson peashooter win all thirteen of the American Motorcycle Association National Championship dirt track races. Petrali breaks four records in the process.    
1936 Harley-Davidson introduces the EL, an overhead valve, 61 cubic inch powered bike. With increased horsepower and bold styling changes, the motorcycle quickly earns the nickname of "Knucklehead," due to the shape of its rocker boxes. The same year, the Motor Company introduces a 80 cubic inch side valve engine.    
1937 The first WL models are produced. Joe Petrali sets a new land speed record of 136.183 mph on a modified Harley-Davidson 61 cubic inch overhead valve-driven motorcycle. . The same day, he also breaks the record for 45 cubic inch engine motorcycles.    
1940 Babe Tancrede is the winner at the Daytona 200, riding a WLDR model.    
1941 America is plunged into World War II. Production of civilian motorcycles is almost entirely suspended in favor of military production. The Service School is converted back to the Quartermasters School for the training of military mechanics.    
The FL series premieres.    
1942 Among other motorcycles made for the Army, H-D produces the unique XA 750, a motorcycle with horizontally opposed cylinders and shaft drive, designed for desert use. The contract is cancelled early due to war combat moving out of North Africa. Only 1,011 XA's are built.    
1943 Harley-Davidson receives the first of its four Army-Navy "E" Awards for excellence in wartime production. Overseas, many American servicemen get their first exposure to Harley-Davidson motorcycles, something they would not forget when they would return stateside.    
1945 World War II ends, and Harley-Davidson has produced almost 90,000 WLA models for military use. Wasting no time, production of civilian motorcycles resumes in November.    
1946 Harley-Davidson introduces the 45 cubic inch flathead WR racing motorcycle. It proves to be one of the best racing motorcycles ever built.    
1947 Attendees at the year's Dealers Convention in Milwaukee are given a train ride to a "secret destination," which turns out to be the newly purchased plant on Capitol Drive. The plant was formerly the A.O. Smith Propeller Plant, created during the war. Harley-Davidson uses the plant as a large machine shop, shipping the new parts to Juneau Ave. for final assembly.    
Harley-Davidson begins selling what will become the classic black leather motorcycle jacket.    
Harley-Davidson dirt track racer Jimmy Chann wins the first of three consecutive AMA Grand National Championships.    
1948 New features are added to the 61 and 74 overhead valve engines, including aluminum heads and hydraulic valve lifters. Also new are the one piece, chrome plated rocker covers shaped like cake pans. The nickname "Panhead" only seemed logical.    
Production of American-made lightweight motorcycles begins with the model S. Various versions will be sold until 1966.    
1949 Hydraulic front forks first appear on the new Hydra-Glide models.    
1950 Larry Headrick wins the AMA Grand National Championship for Harley-Davidson in dirt track racing.    
Harley-Davidson riders win 18 of 24 National Championships and set six new racing records.    
1952 The side-valve K model is introduced with an integrated engine & transmission to compete with smaller, sportier motorcycles coming mainly from Great Britain. The K will eventually evolve into the Sportster.    
1953 Harley-Davidson celebrates its 50th Anniversary in style. An attractive logo is created, depicting a "V" in honor of the engine which had brought the Company so far, with a bar overlaid reading "Harley-Davidson" and the words, above and below, "50 years--American made." A medallion version of this logo is placed on the front fenders of the 1954 models.    
Hendee Manufacturing, the creator of the Indian motorcycle, goes out of business. Harley-Davidson would be the sole U.S. motorcycle manufacturer for the next 46 years.    
1954 Dirt track racer Joe Leonard wins the AMA Grand National Championship. Over the next eight years, the Grand National Championship will be won by Harley-Davidson racers.    
1955 This year begins a seven-year consecutive run of victories at the Daytona 200. The victories will be shared by racers Brad Andres, Johnny Gibson, Joe Leonard and Roger Reiman. All ride Harley-Davidson KR models. Reiman's victory in 1961 is on the new speedway course.    
1956 The new young star Elvis Presley poses for the cover of the May Enthusiast sitting on a 1956 model KH.    
1957 The motorcycling public met a new motorcycle called the Sportster®. It premiers as a 55 cubic inch overhead valve engine, and within one year of its debut, becomes known as the first of the "Superbikes." Another Harley-Davidson tradition and legend is born.    
1960 The Harley-Davidson Topper motor scooter is introduced and is the only scooter platform the Motor Company ever produced.    
Harley-Davidson purchases a half interest in Aeronatica-Macchi, forming Aermacchi Harley-Davidson, a European division that will produce small, single cylinder motorcycles.    
In this year of Brad Andres' 1st place finish at the Daytona 200, the top 14 finishers are also riding Harley-Davidson 750 KR models.    
1961 Introduction of the Sprint model.    
1962 Harley-Davidson purchases 60 percent of the stock in the Tomahawk Boat Manufacturing Company. H-D recognizes the rising relevance of fiberglass in motorcycle production, and begins manufacturing its own components. As a result, the Tomahawk Division is established and is operational as a Harley-Davidson facility by 1963.    
1963 Ralph White resumes the winning of the Daytona 200 for Harley-Davidson, again on a 750 KR motorcycle.    
1964 Roger Reiman wins the AMA Grand National Championship for Harley-Davidson. Reiman also scores the first of back-to-back Daytona 200 victories on a 750 KR.    
The three-wheeled Servi-Car becomes the very first Harley-Davidson motorcycle to receive an electric starter.    
1965 The Electra-Glide® replaces the Duo-Glide and is updated with electric starter. The Electra-Glide is the first FL available with electric start, and the Sportster® line would receive electric starters soon after.    
In a Streamliner powered by a 250cc Sprint CR racing engine, George Roeder shatters the speed records for Class A and Class C runs, averaging 177 miles per hour.    
Harley-Davidson dirt track racer Bart Markel wins the AMA Grand National Championship in 1965 and 1966.    
1966 The first of the "Shovelhead" engines is introduced on the Electra-Glide models, replacing the Panhead.    
1968 Cal Rayborn wins the first of back-to-back victories at the Daytona 200 on a 750 KR model.    
1970 In consideration of new AMA rules for Class C racing, a new Sportster®-based motorcycle, the XR 750 racer is introduced.    
On the Bonneville salt flats near Wendover, Utah, racer Cal Rayborn breaks the world record for land speed set by a motorcycle. The vehicle is a sixteen foot streamliner powered by a single Sportster engine, and averages just over 265 mph.    
1971 In response to the customizing craze, Harley-Davidson introduces the FX 1200 Super Glide®, which combined a sporty front end (similar to that of the XL series) with the frame and powertrain of the FL series. A new class of motorcycle, the cruiser, is born.    
First year of Harley-Davidson snowmobile production.    
1972 The new, more powerful, more reliable aluminum alloy XR-750 debuts. It becomes the dominant dirt track racer through the next three decades. Dirt track racer Mark Brelsford wins the AMA Grand National Championship on the XR-750 this year.    
1973 Motorcycle production is upgraded when all assembly operations are moved to a modern 400,000 square foot plant in York, Penn. All other production operations remain in Milwaukee and Tomahawk. The Capitol Drive plant in Milwaukee begins production of engines.    
1975 The first of four more consecutive years of Harley-Davidson AMA Grand National Championships in dirt track racing. Gary Scott wins in 1975. The following three years are won by racing legend Jay Springsteen.    
1977 Harley-Davidson introduces the FXS Low Rider® to the public in Daytona Beach. With drag style handlebars, unique engine and paint treatments, the Low Rider lives up to its name by placing the rider in a lowered seating position than was typical. Later in the same year, Willie G. Davidson's dynamic version of the Sportster, the Cafe Racer, is released.    
1979 Introduction of the FXEF Fat Bob, "Fat" because of the dual gas tanks, "Bob" for the bobbed fenders.    
1980 Harley-Davidson debuts the FLT with its vibration dampening, rubber-isolated drivetrain and unique trailing front fork. The FLT also debutes an engine and five-speed transmission that are hard bolted together.    
A kevlar belt replaces the chain as the final drive. The belt is cleaner running, and needs less adjustments and maintenance. It isn't long before belt final drive is standard on all Harley-Davidson® motorcycles.    
The AMA Grand National Championship in dirt track racing goes to yet another Harley-Davidson racer, Randy Goss.    
In honor of the historic Sturgis motorcycle rally, Harley-Davidson releases the FXB Sturgis model, employing belt drive, black chrome appointments and 80 cubic inch engine.    
The FXWG Wide Glide is introduced for the 1980 model year.    
1981 On February 26, thirteen Harley-Davidson senior executives sign a letter of intent to purchase Harley-Davidson Motor Company from AMF. By mid-June, the buyback is official, and the phrase "The Eagle Soars Alone" becomes a rallying cry.    
Scott Parker begins racing for team Harley-Davidson on the AMA dirt track circuit. He will become the most successful racer in Harley-Davidson history, accumulating 93 career victories and, more incredibly, winning 9 Grand National Champion titles in a 10 year period.    
1982 More innovations demonstrate a new commitment to quality, such as the FXR/FXRS Super Glide® II with its rubber-isolated, five-speed powertrain and the welded and stamped frame for the new Sportster® models.    
The top three finishers in the AMA Grand National Championship are Ricky Graham, Jay Springsteen and Randy Goss. This begins a two year run of dirt track Championship wins for Harley-Davidson. Goss takes the Championship in 1983.    
  The Materials As Needed (MAN) application is introduced to production. Generally, this means that parts and raw materials are purchased and built only as they are required. This dramatically lowers production costs and improves quality.    
1983 Harley-Davidson successfully petitions the International Trade Commission (ITC) for tariff relief, which is granted April 1, 1983. The tariff, scheduled to end five years later, is placed on all imported Japanese motorcycles 700cc or larger as a response to Japanese motorcycle manufacturers stockpiling inventories of unsold motorcycles in the United States.    
One of Harley-Davidson's most unique endeavors begins: Harley Owners Group®. Fondly referred to as H.O.G.®, the Group immediately becomes the largest factory-sponsored motorcycle club in the world. Within six years, H.O.G. membership soars to more than 90,000. By the year 2000, it exceeds 500,000 members.    
Dirt track racer Randy Goss wins the AMA Grand National Championship this year.    
1984 Harley-Davidson unveils the 1340cc V²® Evolution® engine on five models including the all-new Softail®. The result of seven years of development, the Evolution engine produces more power at every speed, runs cooler, cleaner and is oil-tight. Also witnessed is the debut of the Softail design and its trend-setting method of "hiding" the motorcycle's rear shock absorbers.    
1986 In another bold styling and engineering move, Harley-Davidson releases the Heritage Softail®.    
The Motor Company is listed on the American Stock Exchange, the first time Harley-Davidson is publicly traded since 1969, the year of the AMF merger.    
The Sportster® motorcycle line receives the Evolution V-twin engine.    
To diversify its holdings, Harley-Davidson purchases Holiday Rambler Corporation, producer of quality motor homes.    
1987 Harley-Davidson is listed on the New York Stock Exchange.    
Harley-Davidson makes both business and American history. H-D petitions the International Trade Commission for early termination of the five-year tariffs on heavyweight motorcycles. In effect, the move demonstrated confidence in H-D's ability to compete in the marketplace.    
Harley-Davidson begins the "Buy Back Program," for the XLH 883 Sportster, which offers full trade-in value within two years on either a model FL or FX.    


Upon its introduction, the FLSTF Fat Boy® almost instantaneously becomes a modern legend of motorcycle design.    
1991 Installation of a $31 million state of the art paint facility begins at the York, Penn., factory. It becomes fully operational in 1992.    
The Dyna line of motorcycles debuts with the 1991 FXDB Dyna Glide Sturgis®.    


Harley-Davidson buys a minority interest in the Buell Motorcycle Company. Erik Buell created the Company to manufacture American sport motorcycles using Harley-Davidson® XL 883 engines.    


Harley-Davidson celebrates its 90th Anniversary in Milwaukee with a Family Reunion. An estimated 100,000 people ride in a parade of motorcycles.    


Harley-Davidson enters Superbike racing with the introduction of the VR1000, a dual overhead cam, liquid-cooled motorcycle.     
1995 The classically-styled FLHR Road King® is introduced.    
The 30th Anniversary Ultra Classic® Electra Glide® becomes the first production Harley-Davidson motorcycle to include sequential port electronic fuel injection.    


A new, state-of-the-art Parts and Accessories Distribution Center opens in Franklin, Wis. By the beginning of 1997, all inventory is moved from the original warehouse at Juneau Avenue to the new 250,000-sq.-ft. facility.    
1997 A new 217,000-sq.-ft. Product Development Center opens next to the Capitol Drive plant in Milwaukee. The building is dedicated to Willie G. Davidson.    
Powertrain Operations at Capitol Drive expanded its capacity by moving FL engine and transmission production to a newly purchased plant located in Menomonee Falls. XL engines and transmissions, as well as Genuine Parts Manufacturing, remain at Capitol Drive.    
A new 330,000-sq.-ft. plant in Kansas City produces its first Sportster.  
1998 Harley-Davidson celebrates its 95th Anniversary. 140,000 plus riders are warmly received by Milwaukee to help with the celebration.    
A new assembly facility opens in Manaus, Brazil, the first operations outside of the U.S.    
Harley-Davidson buys a remaining 49% interest in Buell Motorcycle Company. Erik Buell is named Chairman of Buell operations.    
1999 All 1999 model year big twins receive the new Twin Cam 88® engine.    
2000 The FXSTD Softail® Deuce™ is introduced to the immediate delight of riders and the motorcycle media.    
The 2000 model year Softail® and Dyna Glide models are outfitted with the Twin Cam 88B™ engine, a counter-balanced version of the Twin Cam 88.    
Fuel injection is unveiled as a feature new to the Softail line of motorcycles for the 2001 model year.    
2001 The VRSCA V-Rod® is introduced for the 2002 model year. Inspired by the VR-1000 racing motorcycle, the V-Rod is Harley-Davidson's first motorcycle to combine fuel injection, overhead cams and liquid cooling, and delivers 115 horsepower.    
Harley-Davidson Racing announces the latest addition to the team: 17 year old Jennifer Snyder, the first woman to win a national event in the Formula USA National Dirt Track Series.    
Harley-Davidson announces expansions at the Product Development Center (Milwaukee), as well as Tomahawk, WI, and York, PA, facilities.    
2002 The all-new Buell® Firebolt® storms onto the scene.    
The Open Road Tour debuts in Atlanta, GA, in July to celebrate the upcoming Harley-Davidson 100th Anniversary.    
2003 Buell Motorcycle Company unleashes the Lightning® XB9S.    

A (1926): SV/OHV 21-inch single (magneto ignition)
A (1960): TS (two stroke) 165CC Topper scooter
B (1926): SV/OHV 21-inch single
B (1955): TS 165CC single
/B: Belt-drive Sturgis model (ex. 1982 FXB)
C (1920): i.o.e. 35-inch single, special order
C (1930): SV/OHV 30.5-inch single
/C: Custom, Classic or Caf
/CH: Magneto Sportster (ex. 1958 XLCH)
D (1929): SV 45-inch twin
/D: 74-inch engine (ex. 1921 JD)
/D: Extra power (ex. 1930 DLD)
/D: Dyna Glide frame (ex. 1991 FXDB)
/DG: Disc Glide (ex. 1983 FXDG)
E (1936): OHV 61-inch twin
/E: Electric starting (ex. 1964 GE, 1974 FXE)
/E: Police engine (ex. 1953 FLE)
F (1920): i.o.e. 61-inch magneto ignition (dating from 1914)
F (1941): OHV 74-inch twin
/F: Battery ignition flat twin (ex. 1921 WF)
/F: Footshift (ex. 1952 FLF)
G (1933): SV 45-inch Servi-Car
/H: Larger engine (ex. 1936 80-inch VHL, 1955 55-inch KH)
/H: More powerful engine (ex. 1955 FLH)
I: Fuel injection (ex. 1995 FLHTCI)
J (1920): i.o.e. 61-inch twin (dating from 1915)
/J: Magneto ignition flat twin (ex. 1921 WJ)
/K: More powerful K model (ex. 1955 K11K)
L (1920): Single-passenger sidecar (dating from 1915)
/L: Higher compression engine (ex. 1936 EL)
M (1920): Commerical sidecar (dating from 1915)
M (1965): TS 50CC single, Aermacchi
/N: Newspaper delivery sidecar (ex. 1929 MN)
/N: Nostalgia (ex. 1993 FLSTN)
/O: Open-body commercial sidecar (ex. 1926 MO)
/P: Police model
Q (1920): Two-passenger sidecar chassis (dating from 1918)
R (1932): SV 45-inch twin
/R: Rubber-mount FX model (ex. 1982 FXR Super Glide)
/R: Pseudo-racing model (ex. 1983 XR-1000)
/R: Racing model (ex. 1952 KR)
S (1926): OHV 21-inch, for racing purposes
S (1948): TS 125 single
/S: Sport (ex. 1978 FXS and XLS)
/S: Sidecar use (ex. 1936 ES)
T (1921): Twin-cylinder racer
/T: TS 165 single (ex. 1953 ST)
/T: Touring (ex. 1977 XLT, 1980)
U (1937): SV 74-inch twin
V (1930): SV 74-inch twin
V (1994): DOHC 61-inch twin, for Superbike racing
W (1920): SV 36-inch flat twin (dating from 1919)
W (1937): SV 45-inch twin
/WG: Wide Glide (ex. 1980 FXWG)
X (1957): OHV 55-inch twin (usually used with L; i.e. XL)
Y: Only letter never used
Z (1973): TS 90CC single, Aermacchi

Here are some models styles to go by.

XLH Sportster 883
XLH Sportster 883 Hugger
XLH Sportster 1200
XL 1200C 1200 Custom
XL 1200S 1200 Sport
FXD Dyna Super Glide
FXDL Dyna Low Rider
FXDS-CONV Dyna Convertible
FXDWG Dyna Wide Glide
FLSTS Heritage Springer Softail
FXSTS Springer Softail
FXSTC Softail Custom
FLSTC Heritage Softail Classic
FLHR/FLHRI Road King / Road King Fuel Injected
FLHT Electra Glide Standard
FLHTC/FLHTCI Electra Glide Classic / Electra Glide Classic
FLHTCUI Ultra Classic Electra Glide Fuel Injected