The Topper had a 165 cc (10.1 cu in) single-cylindertwo-stroke engine mounted horizontally between the floorboards.[8] The engine required a premixed gasoline/oil mixture. The starter was of the rope-recoil type similar to lawn mowers[1][8][9] or the Lambretta E model.[10] Unlike most scooters with enclosed engines, the Topper's engine did not have a cooling fan.[2][5][6] It was expected that the low, horizontally mounted engine would be cooled by air passing under the scooter,[2] but some Toppers developed overheating problems.[5] The engine used a reed valve in its induction system.[3]
The engine powered a continuously variable transmission[2][9] called "Scootaway Drive"[3][9] that included a safety device that did not allow the scooter to move from rest at engine speeds higher than 1800 rpm.[8] Final drive was by an exposed roller chain.[3][8]
The Topper had 5 inch internal expanding drum brakes on both wheels.[3] The front brake was controlled by a hand lever[2][3] on the left handlebar[1] with a parking brake lock;[1][3] the rear brake was controlled by a pedal.[2][3]
The front body, front fender and floorboards of the Topper were made of stamped steel, and the engine cover and body were made of molded fiberglass.[11] Storage space was provided under the seat; the manufacturer suggested storing extra containers of two-stroke oil there.[1]
Development
The main complaint from Topper owners was with the "Scootaway Drive" continuously variable transmission. Road grime would get into the transmission and cause the belt to slip.[1] A new transmission, with the primary drive sealed in an oil bath, was introduced for 1961.[4]
The Topper H was introduced in 1961 (sold through 1965) with a new alloy cylinder head that increased the compression ratio to 8.0:1, a reusable foam air filter, and revisions to the cylinder ports and air intake tube.[4]
A detuned version of the Topper was also available, with the power restricted to 5 hp (3.7 kW).[12] This was advertised as the "Topper U".[13] The detuned Topper was made to comply with laws in some states in the United States that allowed motorcycles with rated engine power below a stated maximum to be operated without a license[1] or to be operated on a special license by riders at a younger age than would be allowed a regular motorcycle license.[12]
Dan, Michael (2007-05-01). The A-Z of Popular Scooters & Microcars: Cruising in Style!. MBI Publishing. p. 138. ISBN978-1-84584-088-4. The enclosed engine did not have a cooling fan which, on occasion, led to overheating problems.
Wright, David K. (1987) [1983]. "Chapter Three: Iron". The Harley-Davidson Motor Company: An Official Eighty-Year History (Second ed.). Motorbooks International. pp. 46–97. ISBN0-87938-245-7. William H. Davidson told directors that 10,000 were made and sold in the first seven months of 1947.
Online
"Harley-Davidson Timeline 1960s". Harley-Davidson Timeline. Harley-Davidson. 2015. Archived from the original on 2006-10-29. Retrieved 2015-04-19. The Harley-Davidson Topper motor scooter is introduced and is the only scooter platform the Motor Company ever produced.
The Auto Editors of Consumer Guide (2007-09-18). "1963 Harley-Davidson Topper". How Stuff Works. Archived from the original on 2009-12-03. Retrieved 2015-04-19. Its 165-cc two-stroke single was started with a recoil starter, like a lawn mower, and drove through a variable-ratio automatic transmission called Scootaway Drive.{{cite web}}: |author= has generic name (help)
"Lambretta Model E". Lambretta Club of Great Britain. Archived from the original on 2010-06-23. Retrieved 2012-12-24. To start the scooter a pull cord (like that found on chain saws) was mounted in front of the magneto, the ignition on the E could be advanced and retarded for ease of staring (sic) on the pull cord, this ensured the machine did not 'kick back' injuring the person while starting it.
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