Harley-Davidson Flatheads 1929-1974The baby brother of Harley-Davidson's venerable Big Twin line, the 45 cubic inch side-valve engine may lack the grunt of its larger siblings, but the 25-horsepower middleweight compensates nicely with reliability that would shame a John Deere tractor. This is mainly due to the flathead's extremely simple design, which was first created in 1929 and served well until its demise in '74. As a result of this long, virtually unchanged production run (the three-wheeled Servi-Car did receive electric starters in '64) the three-speed 45s were easy to maintain and proved incredibly popular with police departments as traffic-control vehicles, but also with delivery firms such as florists and auto parts stores. In either the 74 or 80 cubic inch UL and ULH configurations, the flathead motor shared the 45's dry sump lubrication and then-revolutionary circulating oil pump, along with its jockey shift three-speed transmission.
Larger flatheads are discernible from their smaller brothers by their larger cooling fins, while performance is modest by modern standards. With single-sided drum brakes front and rear, expect stopping to be a gradual affair at best. Flatheads are extremely rare on the used motorcycle market, and most of the two-wheeled 45s currently on sale are actually highly modified Servi-Cars, so make sure the frame and engine numbers match. Most attractive are WWII-era WLA flathead 45 models, painted in olive drab and dressed up for U.S. military service, though if you are fortunate enough to locate an original Army 45, expect to pay $30,000-$50,000.
Harley-Davidson E, El, And Fl Knucklehead 1936-1947This is the engine design that spawned every consecutive Harley-Davidson powerplant, up to and including the water-cooled V-Rod. Graced with voluptuous lines and period-perfect art deco styling, the original knucklehead Harleys were among the most beautiful motorcycles every to leave Milwaukee, and as a result are one of the most sought-after by collectors. The rigid frame knucklehead in original form, however, is tough to find, as many have either been chopped or had their donor engines grafted into aftermarket frames with swingarm suspension. Ironically, the jockey-shift setup on knucklehead models was often discarded during the life of the motorcycle in favor of the easier-to-operate hand-clutch/foot shift system. However convenient, this is a modification that frustrates vintage bike enthusiasts who must then try and source the original parts. With a Springer frontend and a rigid rear, cracked and repaired frames are not uncommon, but if welded properly they should not be an issue. Krummel says not to be put off by a trace or even a small pool of oil collected beneath a knucklehead, as the porous, sand-cast engine cases seeped a small amount of 40-weight by design; the four-speed transmission is moved fore or aft to adjust a knucklehead's final drivechain, and the tin primary cover also "breathes" a certain amount of lubricant due the primary chain's lubrication system. In stock form, a well-maintained knucklehead will run all day at 70 mph and will reach a top speed of around 95 mph, but most owners cherish such rare, valuable machines and content themselves with puttering along country lanes as far less challenging velocities.