Harley-Davidson Small Twin Flathead

Harley-Davidson's small twin flathead, or "45," debuted in 1929 as the Model D. It was Harley's answer to the successful Indian Scout. The engine design evolved through the R-series and ultimately became the long-running W-series in 1937, with production for the three-wheeled Servi-Car continuing all the way to 1973. Its most famous application was the WLA, the ubiquitous military motorcycle of World War II.

These bikes are popular with collectors for their classic pre-war looks and mechanical simplicity. The 45 cubic inch flathead is a durable and reliable engine, and a huge parts supply exists thanks to its long production run and military service. WLAs are particularly sought after for their historical connection, but civilian models like the WL and the Servi-Car also have strong followings.

The market for small twin flatheads is accessible but has a high ceiling for top examples. While project bikes can be found for a few thousand dollars, restored and historically significant examples command high prices. The average sale price around $18,763 suggests that most traded bikes are solid, rideable examples rather than concours-level restorations or non-running projects.

Prices range from $2,500 for non-running projects to $67,000 for exceptionally restored or rare variants.