1931 Harley-Davidson 45ci DL Engine no. 31DL1340

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Lot 155
1931 Harley-Davidson 45ci DL
Engine no. 31DL1340

US$ 24,000 - 26,000
£ 17,000 - 19,000
1931 Harley-Davidson 45ci DL
Engine no. 31DL1340
The Indian Motorcycle Company had successfully campaigned sidevalve engines since 1916. They developed the engines to be practical on the street and the track, repetitively spanking the overhead valve racers of their competitors Harley-Davidson and Excelsior. Sidevalve engines provided a very compact powerplant, and resistant to engine wear from dust and mud since all moving parts were covered. Whereas with overhead valve engines, exposed valves, valve springs and rocker arms were prone to premature wear from the elements. On top of that, they were more expense to manufacture, keep in tune and were inherently noisier. Even most of the automobiles being manufactured at that time used sidevalve engines. There was much pressure from both the industry to stay current and the public for sidevalves.

Harley-Davidson stepped cautiously into the world of sidevalve engines in 1929. The first Forty-fives as they were known used the same frame and gas tank as the 21ci single which suggested that the first planned sidevalve was actually not a middleweight motorcycle but a lightweight of possibly 37ci displacement similar to the first Indian Scout. Sharing the components with the company’s single cylinder motorcycle to save on manufacturing costs affected the engine design. The new engine’s generator was mounted vertically along the left side of the motor allowing detractors to brand the bike, the three cylinder Harley.

Comparisons against the popular Indian 101 Scout 45 were inevitable when the Harley 45 was new. Indian used paired cams for each cylinder while Harley-Davidson incorporated four cams, one for each valve. While more expensive to manufacture, it did allow the Harley rider to perform tuning modifications quickly, or perhaps Harley actually have an eye for racing potential. Harley-Davidson also used a different bore and stroke allowing the new 45 to potentially run harder than its Springfield rival. Using the 21 inch single frame, it ran a separate engine and transmission with a double row primary chain. Indian’s Scout engine had an integrated design that combined the engine and transmission with a sealed gear driven primary all cradled in a rugged double down tube frame. Harley’s powerplant on the other hand could twist in the lightweight frame causing misalignments.

Harley-Davidson brought vast improvements to their middleweight motorcycle in 1931. A brand new frame with welded reinforcements and new forks debuted. One of many updates included a new 7” John Brown Motolamp replacing the ineffective twin bullet lights. It also gained a transmission interlock to prevent gear changes without the use of the clutch, a new tool box to accent the more streamlined appearance of the small twin, a new horn with a chromed sunburst face and a new single pipe muffler replaced the earlier 4-pipe muffler. A new larger rear brake was also carried over from the old 1929 JD model. Customers saw the first use of chrome in 1931 however it remained for only small parts initially.

This 1931 Harley-Davidson DL represents the high compression sports model which sold for $310 when new and accounted for 1,306 motorcycle sales that year, double the sales of the next most popular model. This particular motorcycle was nicely restored by Mike Ryall’s Kustom Bike Shop in 2003 with a paint scheme simulating Harley-Davidson’s popular art deco swirl design and is offered with a title.

Saleroom notices

  • This bike's Canadan title has an incorrect engine number listed on it. This number will be corrected prior to delivery to the buyer.
1931 Harley-Davidson 45ci DL Engine no. 31DL1340
1931 Harley-Davidson 45ci DL Engine no. 31DL1340
1931 Harley-Davidson 45ci DL Engine no. 31DL1340
1931 Harley-Davidson 45ci DL Engine no. 31DL1340
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