Harley-Davidson 1937 Model UL — Flathead
In a previous post, I briefly touched on a remarkable collection of classics in the northwest and how I was most fortunate to interview the family and learn more about an inspirational man with a genuine love of wrenching on vintage motorcycles.
In this post, I’m taking a deeper dive on the first (frame-up) restoration in that collection — a 1937 Harley-Davidson Model U-Series Flathead.
According to Harley-Davidson, the UL production in 1937 was 2,861 units and the motorcycle sold for $395 or the equivalent purchasing power of about $7,100 in 2020.
Harley-Davidson 1937 Model UL — Teak Red
There is nothing more alarming than a motorcycle that has been built, modified or customized by someone of dubious talent and knowledge. All it takes is a quick spin around Craigslist, searching for the terms “project,” “bobber,” “custom” or “café racer” to turn up any number of bikes that will have you saying WTF.
Many times these projects are started with the best of intentions, but the absolute worst are the ones that are started in an attempt to make a quick buck, or resurrect a wadded up bike.
However, this ’37 wasn’t someone else’s project. It would need help bringing her back to life, but it had all the original sheet metal, flathead engine, transmission, speedometer, leather saddle bags, solo seat and more.
Instruction Manual
Bob spent several years on the identification, collection of manuals and parts search for this exceptionally high caliber restoration. He completed the motorcycle restoration in 1975 and was often seen riding it at various antique club events through-out the years. The motorcycle has lots of crowd-pleasing brightwork, is an excellent runner with showy pieces of Art Deco styling and old school looks.
A fascinating backstory is the original restoration color on this ’37 was Olive Green with Black striping. Bob loved spending time with his grandkids who were all very involved in taking things apart including motorcycles. It started with bicycles then mini-bikes and later on with motorcycles and automobiles. In his workshop, he’d show them how to take apart things and repair them — the correct way — with the correct tools! Several years after completing this restoration, he decided to work on a project with his grandkids and taught them how to disassemble the ’37 inorder to repaint the sheet metal Teak Red. Those kids meant the world to him and passing down his tradesman skills might be his legacy.
1937 Harley-Davidson Model UL
The ’37 is an excellent example of the — Flathead Engine — a charming, honest, beautiful bike that doesn’t rely on diaper-shined chrome or flawless paint to impress. Named for its flat-topped, vented cylinder heads, the side valve-equipped (using tappets) 74 cubic inch V model Big Twin actually came out in 1930, but in 1937 the U-series motors were of dry-sump oil design.
At first flatheads seemed out-of-step or backwards compared to higher-horsepower overhead-valve designs. But, out in the real world, the “flatty’s” broad spread of torque, less clattery operation and cheaper buy-in continued to win over riders. The 74 cubic inch “F” motor has a 4-speed tank-shift transmission and a Linkert M51 mechanical butterfly carburetor.
The teardrop-shaped fuel tank is adorned with an instrument panel (dubbed the “Cat’s Eye”) that bundled all the gauges into one graceful package. It even has the rare dash panel with the oil and amperage indicators.
1937 Harley-Davidson Model UL — aka “Cat Eye”
The Big Twin model was built in part to compete with the 74 cubic inch Indian Chief. The U and UL models featured 74 cubic inch power plants, and the UH and the ULH models were outfitted with 80 cubic inch engines. The 80 cubic inch models were produced until 1941, and the 74 cubic inch U and UL models were in production until 1948. The three-wheeled Harley-Davidson Servi-Cars made from the early 1930s through 1975, were powered by flathead engines during their entire run of production.
One of the most notable improvements found on the ’37 U-series, was the new design, which recirculates the oil from the oil tank, through the engine and back to the oil tank. Up until 1936, all Harley-Davidson motorcycles used “total loss” systems, which essentially ran the oil from the oil tank, through the engine and ultimately onto the ground. Thus the nickname: “road oilers.”
1937 Harley-Davidson Model UL
The valves are actuated by four gear-driven camshafts (one per valve) and used adjustable tappets to maintain precise spacing between the cam lobs and the valve stems. Although the cylinder heads don’t contain any moving parts, they do play an important role in cooling the engine. Initially Harley-Davidson outfitted the U-series motors with cast iron cylinder heads, but soon switched to forged aluminum alloy heads with deeper cooling fins for improved cooling. The engine has brass spark plug inserts added to address the former engines’ problems of stripping threads. This motorcycle doesn’t have them, but at the time customers could opt for optional silicon aluminum heads.
1937 Harley-Davidson Model UL
Fuel and air are fed into the motor using a single Linkert carburetor, which is positioned on the left side of the motorcycle. Harley reversed this arrangement for its overhead motors, which all have right side carburetors. Exhaust was routed and expelled via a single fishtail muffler on the right side.
The primary chain, located on the left-side, transmits power from the engine to the 4-speed transmission. The transmission is hand shifted via a lever mounted on the left side of the fuel tank and the clutch is controlled with a foot pedal. A secondary chain transmits power from the transmission to the rear wheel using a brake drum mounted sprocket.
The front and rear drum brakes are engaged manually with no hydraulic assistance. The front uses a cable to connect a right side mounted hand lever to the left side mounted drum. The rear uses a series of adjustable rods to engage the motion of the right side brake pedal through the frame and out to the left side mounted rear drum.
1937 Harley-Davidson Model UL
The ’37 Model UL rides on a “hardtail” frame. Basically, there is no rear suspension. The sprung solo seat helps offset the lack of any rear suspension, and the “Springer” front end is the main suspension on the Model UL. It’s a two piece element that uses six external springs on the top and moveable rocker arms on the bottom. The springs absorb impacts while the rocker arms permit vertical movement of the front axle.
The left hand grip operates the engine timing, allowing a rider to retard the timing for easy starting and advance the timing for normal running. The horn button and the high/low beam switch for the headlight are located on the left side handlebar as well.
1937 Harley-Davidson Model UL
Shifting the 4-speed transmission is accomplished using a hand lever that is attached to the left side of the fuel tank. A shift gate helps the rider find the gears without skipping gears when shifting. The foot operated clutch, known as a “rocker clutch” is used to engage and disengage the clutch. All Harley’s use the “toe to go” set up where pressing the clutch pedal forward with the toe engages the clutch and pushing the pedal back with your heel disengages the clutch. A friction disc is used to keep the clutch pedal in the heel back position, so that the rider does not have to keep their foot on the pedal when the motorcycle is stopped.
It’s challenging to explain the ’37 Harley-Davidson Model UL mystique. There is both excitement and apprehension in managing the technique of a rocker clutch and tank mounted shifter. Adding to the rider challenge is counteracting the heavy Springer front-end during a corner. Stability, if there is such a thing on this model, is a complicated matter and the manufacture of motorcycles in the 1930’s were very reluctant to talk about it.
In the fast moving world we live in today, it’s difficult to wrap your head around the bicycle-like origins starting in the Davidson family’s backyard more than 116-years ago. If we had the luxury of going back in time, we could ask the young inventors, but I’d anticipate the founding group would be exceptionally proud of Bob’s restoration treasure and the enduring craftsmanship on “their” 1937 Model UL.
UPDATED: March 8, 2020 — The third post on this vintage motorcycle collection is: Every Restored Motorcycle Has A Story — The 1913 Single
UPDATED: October 21, 2020 — The fourth post on this vintage motorcycle collection is a deep dive on an original 1916 Indian PowerPlus (HERE).
Author Comments: Although my name appears on the post, it takes a “village” to pull together this type of information. I’m not only delighted to be working with Bob’s family, I also get the honor of thanking them here.
Photos taken by author and courtesy of Harley-Davidson.
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