The 1937 Harley-Davidson Model UH Flathead holds a legendary status in prewar American motorcycling, introducing the heavy-duty, high-capacity pinnacle of the "U-Series" Big Twin lineup.

Engineered explicitly for sidecar hauling, commercial use, and high-speed highway cruising, this massive 80 cubic-inch (1311cc) side-valve V-twin prioritized unrelenting torque and industrial-grade reliability. It debuted during a transformative era when Harley-Davidson completely overhauled its engineering practices to meet the needs of long-distance riders.

This example is highly customized, so the following production information and technical specs pertain only to stock models may be different from the bike before you.

Historical Significance & Evolution

• The Debut of the 80ci U-Series: Launched in 1937 as part of the brand-new U-series to replace the outgoing VL line, the UH variant offered an enlarged displacement alternative to the standard 74ci Model U. It was targeted directly at riders requiring maximum low-revving lugging power.

• The Dry-Sump Breakthrough: Before 1937, Harley-Davidson flatheads relied on messy "total-loss" oil systems. The 1937 UH helped pioneer a recirculating dry-sump oiling system, completely modernizing engine lubrication, drastically improving cooling, and lowering routine oil consumption.

• Prewar Rarity: While the smaller 45ci WL and 74ci U models were built in massive quantities, the premium 80ci UH and high-compression ULH models were produced in far fewer numbers, making authentic 1937 first-year variants exceedingly rare and highly prized by prewar preservationists today.

Production Run

1937–1941 (The 80ci Big Twin flathead solo/sidecar platform had a limited prewar run)

Model Designation

Model UH (Standard compression, built primarily for heavy-duty and sidecar duty)

First-Year Prestige

1937 marked the premier year of the recirculating oiling system and "Cat's Eye" dash

Original MSRP

$415 USD (Base retail price for the premier 1937 80 cubic-inch models)

Technical Specifications

Engine & Powertrain

• Engine Type: 80.1 cu in (1,311cc) air-cooled, four-stroke, 45-degree side-valve V-twin (flathead OHV-style cases with side valves)

• Performance: 39 horsepower @ 4,200 RPM

• Bore & Stroke: 87.3 mm x 109.5 mm (3.437 in x 4.312 in) with a low, reliable 5.0:1 compression ratio

• Induction System: Linkert mechanical butterfly carburetor

• Drivetrain: Tank-mounted hand-shifted 4-speed manual transmission with a foot-operated rocker clutch and a heavy-duty final drive chain

Chassis & Performance

• Suspension: Rigid tubular steel hardtail frame paired with a reinforced trailing-link Springer front fork and a dual-spring solo seat post

• Braking System: Mechanical internal expanding drum brakes (front and rear)

• Curb Weight: Approximately 243 kg (535 lbs) unladen

• Fuel & Oil Capacity: Dual-sided teardrop tanks carrying approximately 4.25 gallons of gasoline and a dedicated integrated oil reservoir tank

• Top Speed: 137 km/h (85 mph) as a solo motorcycle; tailored primarily for sustained 55–60 mph cruising with a heavy sidecar attached