1936–1947 Harley-Davidson Knucklehead Models | EL, FL & Big Twin Reference
This Knucklehead Harley-Davidson Model & Production Reference documents Harley-Davidson motorcycles built from 1936 through 1947, covering the Knucklehead OHV engine family, the expansion of the 61 and 74 OHV twins, wartime production changes, and the transition into the post-war period leading directly to the Panhead. Today the Knucklehead is one of the most collectible and iconic Harley-Davidson engines ever built. For restorers, collectors, and anyone using the Harley VIN Decoder, this page is designed as a year-by-year reference that keeps the model and production data easy to scan while preserving the transition details that make the Knucklehead years one of the most important periods in Harley-Davidson history.
These years mark Harley-Davidson’s first sustained overhead-valve big-twin period, beginning with the 1936 EL and expanding through the arrival of the 74 OHV FL family, wartime civilian interruptions, and the post-war return that leads into the 1948 Panhead era. Because stamped engine numbers identify the year and engine family but do not fully describe every final configuration, this page works best alongside the Model Reference 1903–1969, Paint & Emblems 1936–1965, and the related Harley-Davidson era pages across Riding Vintage. Continue to the 1948–1965 Panhead page for the next evolution of Harley-Davidson OHV big twins.
Use the navigation block below to jump directly to a production year, move to the overlapping or adjacent Harley-Davidson eras, or open the VIN and reference resources that support year-by-year identification work across the full 1903–1969 engine-stamped period.
Quick Navigation
Years:
1936 |
1937 |
1938 |
1939 |
1940 |
1941 |
1942 |
1943 |
1944 |
1945 |
1946 |
1947
Other Eras:
1903–1929 Early Era |
1930–1936 V-Series |
1936–1947 Knucklehead |
1948–1965 Panhead |
1952–1969 K Model & Sportster |
1966–1969 Generator Shovelhead
Resources:
Harley VIN Decoder |
Model Reference 1903–1969 |
Paint & Emblems 1936–1965
Understanding Model Listings
This page is organized by production year. Each year section lists the Knucklehead / OHV models for that year, the other Harley-Davidson models that appeared alongside them, model and VIN notes, and available production figures. Quick Links point to the matching Paint & Emblems 1936–1965 anchor where applicable, and the notes help clarify when sales-model descriptions, sidecar gearing, wartime categories, or other variations do not map one-to-one to the stamped engine number.
Example: EL 61 OHV Twin, Special Sport Solo
- EL = model designation
- 61 = 61 cubic inch engine
- OHV = overhead valve
- Twin = two-cylinder engine
As with other Harley-Davidson eras, configuration details such as sidecar gearing, special-use trim, or wartime production categories do not always appear in the engine number exactly as they appear in sales literature. That is why the listings below work best when paired with the Harley VIN Decoder and the year-specific notes in each section.
Era Overview
The Knucklehead era spans Harley-Davidson’s pre-war OHV development, the expansion of the 74 OHV family, wartime civilian interruptions, and the post-war return that leads directly into the 1948 Panhead era. This page serves as a year-by-year Knucklehead model and production reference, organized around the Knucklehead / OHV motorcycles themselves while also documenting the 45s, side-valve big twins, Servi-Cars, sidecars, package trucks, and other support models that appeared alongside them during the same years.
VIN Information
Knucklehead-era engine numbers identify the year and engine family, but they do not fully describe every final motorcycle configuration. Sidecar gearing designations, special-use variants, and certain marketed model names are not always reflected exactly in the stamped serial number, so the VIN should be used as a starting point rather than a complete description. For complete engine number decoding, see the Harley VIN Decoder. To place decoded motorcycles within the full range of production, use Model Reference 1903–1969.
1936 Harley-Davidson Models
Quick Links: Paint Options
Platform: First Knucklehead year (transition from V-Series)
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo (first year)
- E 61 OHV Twin, Medium Compression
- ES 61 OHV Twin, Sidecar Gearing (Medium Compression)
Other Models
- VL 74 Twin, Special Sport Solo
- V 74 Twin, Medium Compression
- VS 74 Twin, Medium Compression, Sidecar Gearing
- VLD 74 Twin, Sport Solo
- VLDH 80 Twin, Sport Solo
- VH 80 Twin, Medium Compression
- VHS 80 Twin, Medium Compression, Sidecar Gearing
- W 45 Twin, Low Compression
- WL 45 Twin, High Compression
- WS 45 Twin, Sidecar Gearing
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- LE Sidecar
- LS Sidecar
- M Package Truck
- MO Package Truck
- MC Chassis Only
Model / VIN Notes
- 1936 is the first year of the Knucklehead engine (EL), appearing alongside the outgoing V-Series flathead big twins.
- The presence of E and ES alongside EL shows that multiple compression and gearing variants were already offered in the first year.
- This year represents a true overlap period where OHV and flathead big twins are both actively produced.
- For the flathead side of the 1936 transition, see the V-Series reference, where these models are listed alongside the final year of that platform.
Production Numbers
- E — 152
- EL — 1,516
- ES — 26
1937 Harley-Davidson Models
Quick Links: Paint Options
Platform: Early pre-war Knucklehead / Flathead overlap
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- E 61 OHV Twin, Solo, Medium Compression
- ES 61 OHV Twin, Medium Compression, Sidecar Gearing
Other Models
- WL 45 Twin, Sport Solo, High Compression
- WLD 45 Twin, Sport Solo, Extra High Compression
- WLDR 45 Twin, Competition Special
- W 45 Twin, Low Compression
- WS 45 Twin, Low Compression, Sidecar Gearing
- UL 74 Twin, Special Sport Solo
- U 74 Twin, Solo, Medium Compression
- US 74 Twin, Medium Compression, Sidecar Gearing
- ULH 80 Twin, Special Sport Solo
- UH 80 Twin, Solo, Medium Compression
- UHS 80 Twin, Medium Compression, Sidecar Gearing
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- GD Servi-Car, large Commercial Body, less Tow Bar
- GDT Servi-Car, large Commercial Body, with Tow Bar
- GE Servi-Car, large Commercial Body, with Tow Bar, Air Tank and Combination Bumper and Tire Carrier
- LE Sport Sidecar for 61, 74 and 80 Twins
- LS Sidecar for 45 Twin
- M Package Truck with Cover
- MO Package Truck without cover
- LEC LE Chassis only
- LSC LS Chassis only
- MC M/MO Chassis only
Model / VIN Notes
- 1937 is the first year in this reference and shows the 61 OHV Knucklehead coexisting with a very broad flathead and utility lineup.
- Sidecar gearing designations such as WS, US, UHS, and ES are model identifiers, but the sidecar suffix itself is not stamped into the VIN.
- This year also includes an especially wide range of Servi-Car, sidecar, chassis, and package-truck listings.
Production Numbers
- E — 126
- EL — 1,829
- ES — 70
1938 Harley-Davidson Models
Quick Links: Paint Options
Platform: Pre-war refinement
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- ES 61 OHV Twin, Medium Compression, Sidecar Gearing
Other Models
- WL 45 Twin, Sport Solo, High Compression
- WLD 45 Twin, Sport Solo, Extra High Compression
- WLDR 45 Twin, Competition Special
- UL 74 Twin, Special Sport Solo
- U 74 Twin, Solo, Medium Compression
- US 74 Twin, Medium Compression, Sidecar Gearing
- ULH 80 Twin, Special Sport Solo
- UH 80 Twin, Solo, Medium Compression
- UHS 80 Twin, Medium Compression, Sidecar Gearing
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- GD Servi-Car, large Commercial Body, less Tow Bar
- GDT Servi-Car, large Commercial Body, with Tow Bar
- LE Sport Sidecar for 61, 74 and 80 Twins
- M Package Truck with Cover
- MO Package Truck without cover
- MC M/MO Chassis only
- MWC Package Truck Chassis, 57-7/8” Tread
Model / VIN Notes
- 1938 narrows the OHV listings to EL and ES while the surrounding flathead and commercial range remains extensive.
- As in 1937, sidecar gearing suffixes are part of the sales designation rather than the stamped engine number.
- The package-truck and chassis listings also expand with the appearance of MWC.
Production Numbers
- EL — 2,289
- ES — 189
1939 Harley-Davidson Models
Quick Links: Paint Options
Platform: Pre-war refinement
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- ES 61 OHV Twin, Medium Compression, Sidecar Gearing
Other Models
- WL 45 Twin, Sport Solo, High Compression
- WLD 45 Twin, Sport Solo, Extra High Compression
- WLDR 45 Twin, Competition Special
- UL 74 Twin, Special Sport Solo
- U 74 Twin, Solo, Medium Compression
- US 74 Twin, Medium Compression, Sidecar Gearing
- ULH 80 Twin, Special Sport Solo
- UH 80 Twin, Solo, Medium Compression
- UHS 80 Twin, Medium Compression, Sidecar Gearing
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- GD Servi-Car, large Commercial Body, less Tow Bar
- GDT Servi-Car, large Commercial Body, with Tow Bar
- LE Sport Sidecar for 61, 74 and 80 Twins
- M Package Truck with Cover
- MO Package Truck without cover
- MC M/MO Package Truck Chassis Only
- MWC Package Truck Chassis, 57-7/8” Tread
Model / VIN Notes
- 1939 continues the same basic EL / ES OHV structure while preserving the wide flathead and commercial support range.
- The sidecar-gearing suffix remains a model description rather than a VIN-stamped engine feature.
Production Numbers
- EL — 2,695
- ES — 214
1940 Harley-Davidson Models
Quick Links: Paint Options
Platform: Late pre-war
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- ES 61 OHV Twin, Medium Compression, Sidecar Gearing
Other Models
- WL 45 Twin, Sport Solo, High Compression
- WLD 45 Twin, Special, Sport Solo
- WLDR 45 Twin, Competition Special
- UL 74 Twin, Special Sport Solo
- U 74 Twin, Solo, Medium Compression
- US 74 Twin, Medium Compression, Sidecar Gearing
- ULH 80 Twin, Special Sport Solo
- UH 80 Twin, Solo, Medium Compression
- UHS 80 Twin, Medium Compression, Sidecar Gearing
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- GD Servi-Car, large Commercial Body, less Tow Bar
- GDT Servi-Car, large Commercial Body, with Tow Bar
- LE Sport Sidecar for 61, 74 and 80 Twins
- M Package Truck with Cover
- MO Package Truck without cover
Model / VIN Notes
- 1940 is the last pre-war year before the 74 OHV FL family appears.
- The 61 OHV Knucklehead remains the only OHV family listed, while flatheads still dominate the broader range around it.
Production Numbers
- EL — 3,893
- ES — 176
1941 Harley-Davidson Models
Quick Links: Paint Options
Platform: Peak pre-war development
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- E 61 OHV Twin, Medium Compression
- FL 74 OHV Twin, Special Sport Solo
- F 74 OHV Twin, Medium Compression
Other Models
- WL 45 Twin, High Compression
- WLD 45 Twin, Sport Solo
- WLDR 45 Twin, Special Sport Solo
- UL 74 Twin, Special Sport Solo
- U 74 Twin, Solo, Medium Compression
- ULH 80 Twin, Special Sport Solo
- UH 80 Twin, Solo, Medium Compression
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- GD Servi-Car, large Commercial Body, less Tow Bar
- GDT Servi-Car, large Commercial Body, with Tow Bar
- LE Sport Sidecar for 61, 74 and 80 Twins
- M Package Truck with Cover
- MC Chassis Only for Package Truck
Model / VIN Notes
- 1941 is the breakthrough year for the 74 OHV FL / F family in the Knucklehead era.
- The year sheet also reintroduces the lower-compression E model alongside EL, giving the 61 OHV family a broader spread.
Production Numbers
- EL — 2,280
- ES — 261
- FL — 2,452
- FS — 156
1942 Harley-Davidson Models
Quick Links: Paint Options
Platform: Transition year
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- E 61 OHV Twin, Medium Compression
- FL 74 OHV Twin, Special Sport Solo
- F 74 OHV Twin, Medium Compression
Other Models
- WL 45 Twin, High Compression
- WLD 45 Twin, Sport Solo
- UL 74 Twin, Special Sport Solo
- U 74 Twin, Solo, Medium Compression
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- LE Sport Sidecar for 61 and 74
- M Package Truck
- MC Chassis Only for Package Truck
Model / VIN Notes
- 1942 still carries both 61 OHV and 74 OHV Knuckleheads, but civilian production is already being compressed by wartime restrictions.
- The notes for this year also show that sidecar gearing and 45 sidecar arrangements could still be specified even when not represented directly in the serial number.
- The presence of ELA and ELC in the production figures shows how wartime coding and production categories could become more complicated than the simple retail model listings imply.
Production Numbers
- EL — 620
- ELA — 8
- ELC — 44
- ES — 164
- FL — 799
- FS — 107
1943 Harley-Davidson Models
Quick Links: Paint Options
Platform: Wartime production
Knucklehead / OHV Models
- Officially no civilian models were built in 1943
- The exact civilian models are unknown
Other Models
- No confirmed civilian lineup listed
Model / VIN Notes
- 1943 is treated as a wartime interruption year for civilian production.
- The source notes acknowledge that at least a small number of civilian machines may have existed, but the exact model breakdown is not known.
Production Numbers
- No civilian models produced
1944 Harley-Davidson Models
Quick Links: Paint Options
Platform: Wartime / WPB-approved orders
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- E 61 OHV Twin, Medium Compression
- FL 74 OHV Twin, Special Sport Solo
- F 74 OHV Twin, Medium Compression
Other Models
- UL 74 Twin, High Compression Solo
- U 74 Twin, Medium Compression
- LE Sport Sidecar for 61 and 74 Twins
- M Package Truck
- MC Chassis Only for Package Truck
Model / VIN Notes
- 1944 civilian availability is limited to WPB-approved orders rather than a normal retail lineup.
- The year sheets make it clear that 45 models were not officially offered to the public, even though the possibility of extremely limited non-military examples cannot be ruled out completely.
- This is another year where what was technically possible and what was publicly cataloged are not identical.
Production Numbers
- EL — 116
- ES — 105
- FL — 172
- FS — 67
1945 Harley-Davidson Models
Quick Links: Paint Options
Platform: Post-war restart
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- E 61 OHV Twin, Medium Compression
- ES 61 OHV Twin, Sidecar Gearing (Med. Comp.)
- FL 74 OHV Twin, Special Sport Solo
- F 74 OHV Twin, Medium Compression
- FS 74 OHV Twin, Sidecar Gearing (Med. Comp.)
Other Models
- WL 45 Twin, High Compression
- UL 74 Twin, High Compression Solo
- U 74 Twin, Medium Compression
- US 74 Twin, Medium Compression, Sidecar Gearing
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- LE Sport Sidecar for 61 and 74
- M Package Truck
- MC Chassis Only for Package Truck
Model / VIN Notes
- 1945 marks the return of a fuller civilian lineup after wartime interruption.
- The post-war sheets again show the familiar difference between sales/configuration suffixes and the actual stamped VIN.
- The notes for this year also reflect the material and tire constraints still affecting immediate post-war production.
Production Numbers
- EL — 398
- ES — 282
- FL — 619
- FS — 131
1946 Harley-Davidson Models
Quick Links: Paint Options
Platform: Post-war stabilization
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- E 61 OHV Twin, Medium Compression
- ES 61 OHV Twin, Sidecar Gearing (Medium Compression)
- FL 74 OHV Twin, Special Sport Solo
- F 74 OHV Twin, Medium Compression
- FS 74 OHV Twin, Sidecar Gearing (Medium Compression)
Other Models
- WL 45 Twin, High Compression
- UL 74 Twin, High Compression Solo
- U 74 Twin, Medium Compression
- US 74 Twin, Medium Compression, Sidecar Gearing
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- LE Sport Sidecar for 61 and 74 Twins
- M Package Truck
- MC Chassis Only for Package Truck
Model / VIN Notes
- 1946 reflects a more stabilized post-war civilian range built around both 61 OHV and 74 OHV Knuckleheads.
- The same post-war supply and equipment realities still appear in the background notes, but the model structure itself is much stronger than in 1945.
Production Numbers
- EL — 2,098
- ES — 244
- FL — 3,986
- FS — 418
1947 Harley-Davidson Models
Quick Links: Paint Options
Platform: Final Knucklehead year
Knucklehead / OHV Models
- EL 61 OHV Twin, Special Sport Solo
- E 61 OHV Twin, Medium Compression
- ES 61 OHV Twin, Sidecar Gearing (Medium Compression)
- FL 74 OHV Twin, Special Sport Solo
- F 74 OHV Twin, Medium Compression
- FS 74 OHV Twin, Sidecar Gearing (Medium Compression)
Other Models
- WL 45 Twin, High Compression
- UL 74 Twin, High Compression Solo
- U 74 Twin, Medium Compression
- US 74 Twin, Medium Compression, Sidecar Gearing
- G Servi-Car, with Tow Bar
- GA Servi-Car, less Tow Bar
- LE Sport Sidecar for 61 and 74 Twins
- M Package Truck
- MC Chassis Only for Package Truck
Model / VIN Notes
- 1947 is the final Knucklehead year before the Panhead arrives in 1948.
- The model sheet shows a mature post-war lineup with both OHV and side-valve holdovers still present together.
- The sidecar-gearing suffix still functions as a model designation rather than a direct serial-number element.
Production Numbers
- EL — 4,117
- ES — 237
- FL — 6,893
- FS — 401
For the next stage of Harley-Davidson OHV development and the transition to hydraulic lifters and updated engine design, continue to the 1948–1965 Panhead era.
Model Lifecycle Summary
61 OHV Knucklehead Family
- E / EL / ES appear throughout the era, with EL and ES represented in production figures from 1937 onward.
- The lower-compression E model is explicitly listed in the year sheets for 1937, 1941, 1942, and the post-war years.
74 OHV Knucklehead Family
- FL / F / FS appear in 1941 and continue through 1947.
- The arrival of the FL family marks the major expansion of the OHV Knucklehead lineup.
45 Side-Valve Family
- WL-based models are strong in the pre-war years, disappear during wartime restrictions, and return after the war.
74 / 80 Side-Valve Families
- U / UL / US and UH / ULH / UHS anchor the pre-war side-valve big-twin range.
- These lines are sharply reduced or absent during wartime years, then return in more limited form after the war.
Utility and Commercial Support Models
- Servi-Car, sidecar, chassis, and package-truck listings are strongest before the war and return selectively after it.
- These support models are an important part of the Knucklehead-era catalog, even though they are not motorcycle models in the same sense as EL or FL.