|Restore Chapter 2 Serial Numbers and Production||← Up →|
The serial number of your Lightweight is stamped into a raised pad on the left side of the engine crankcase. It's near the front, and turned vertically. There is no serial number on the frame.
Sometime back in the teens, Harley-Davidson standardized their serial number scheme. The serial number is stamped into the engine. This scheme was used until the 1970's when 17-digit Vehicle Identification Number was mandated by law. The format was (using the example of a Knucklehead: 37 EL 2318)
37 EL 2318 | | | | | Sequence Designator | Model Designator Year Designator
The Year Designator was always 2 numeric characters.
The Model Designator varied from 1-to-5 alphabetic characters. The first character letter of the model number indicated the basic engine type. An "E" was a 61 cubic inch overhead valve engine. Additional letters indicated variants of the engine or bike. An "EL" was a High Compression version. An ELP was a high compression Police version.
The Sequence Designator was 4 or 5 numeric characters, representing the order in which a completed bike left the assembly line. The first E model off the assembly line in 1937 was given sequence number 1001. The second E model got 1002, and so on until the end of the year. But the Sequence Designator was shared among variants of the basic engine type. So when the E models started rolling off the assembly line in 1937, they might have been: 37 E 1001, then 37 EL 1002, then 37 ELP 1003, and so on. The American-made lightweights followed this scheme, with a few interesting anomalies.
The U Models
In the 50's and 60's, many states had a "junior driver's license" which allowed 14-year-olds to drive motorcycles under 5 Horsepower. These laws were prevalent in the mid-western states. In those days, Go-Karts and MiniBikes were quite popular, and Harley-Davidson tapped the junior market with special versions of the Model 165, Super-10 and Pacer. These had a U in the Model Designator, e.g. STU and BTU.
The U models had a restricted intake system to drop the horsepower to just below 5, making them eligible for junior licensing restrictions. The 125cc Hummer was already eligible, since it only produced 3.5 hp, but apparantly many people wanted the increased power and style of the Model 165.
The Model 165 STU, produced from 1954 to 1959, had a carburetor with a restricted orifice. The STU's orifice just had a smaller opening than standard ST's. The late 1958 and 1959 STU's are odd - they appear to have used a different cylinder [ 16526-58 - Late 58 & 59 - STU (special) ] instead of a different carburator. This is a matter for further investigation.
The Super-10 (1960-1961) and Pacer (1962-1965) also came in BTU variants. The BTU's achieved the low horsepower effect by using a special cylinder with a restricted intake port rather than a different carburetor. In 1962, the Pacer BTU had the 165cc engine, while the standard Pacer BT had the new 175cc version. It is believed that the 1963-1965 BTU's used the 175cc engine, but this is not certain. See the 1962 detail chapters for more on the mix of 165 and 175cc engines in 1962.
Anomalies - 1962 Models
In 1962, The Pacer and Ranger were 165cc, while the Scat was 175cc. The basic engine was the same, the major differences were the piston and cylinder.
Anomalies - Sequence Designators
1955 through 1959 - the Hummer "B" series, and the Model 165 "ST" series did NOT share sequence numbers. The Hummers started with 55 B 1001, 55 B 1002, and so on. The Model 165 started with 55 ST 1001, 55 ST 1002, and so on.
1960's Models - All the 1960's models used the same basic engine, and the sequence numbers were shared between the different models. So they might have produced 1960 BT 2001, 1960 BTU 2002, 1960 BTH 2003, 1960 BT 2004, and so on. (See next paragraph).
1960's Models - Odd / Even - During the 1960's, Harley played some games with the Sequence Designators. We're not sure why, but we think it was industrial disinformation. Sales of the lightweights were steadily decreasing, and Harley probably wanted competitors to think they were selling far more bikes than they really were. Perhaps you have a different theory.
1960 (an "even" year), serial numbers started at 2001, went to 2999, skipped to 4001 through 4999, then skipped to 6001 through 6488.
1961 (an "odd" year), serial numbers started at 1001, went through 1999, then skipped to 3001 through 3587.
This "even/odd" pattern repeated through the end of production in 1966.
Harley-Davidson production figures are taken from the recent (1993) book "The Legend Begins" published by Harley-Davidson.
Before 2001, the Club kept records of each member and the serial numbers of the bikes they owned. Some members reported a serial number which indicates production above what Harley reports.
|APPROXIMATE PRODUCTION FIGURES|
|1953||ST||Model 165||4220||4232||Serial number 53 BTH 5232 reported|
|STU||Model 165||0||See Note 1|
|1958||B||Hummer||1677||1684||Serial number 58 B 2684 reported|
|1959||B||Hummer||1285||1390||See Note 2|
|ST||Model 165||2311||1907||Serial number 59 ST 3326 reported
Total ST/STU = 2326
|1962||BT||Pacer||1983||745||Serial number 62 BTH 4986 reported
Total BT/BTU/BTH/BTF = 1986
|Last updated: February 15, 2014||← Up →|