HHC: Restore: Chapter 2: Serial Numbers and Production

Serial Numbers

######### 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.

Production Figures

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
YEAR	MODEL	NAME	NUMBER PRODUCED		NOTES
YEAR	MODEL	NAME	H-D	CLUB ESTIMATE	NOTES
1948	S	Model 125	10117	10117
1949	S	Model 125	7291	7291
1950	S	Model 125	4708	4708
1951	S	Model 125	5101	5101
1952	S	Model 125	4576	4576
1953	ST	Model 165	4220	4232	Serial number 53 BTH 5232 reported
1954	ST	Model 165	2835	2835
1954	STU	Model 165	2835	0	See Note 1
1955	B	Hummer	1040	1040
	ST	Model 165	2263	2182
	STU	Model 165	2263	81
1956	B	Hummer	1384	1384
	ST	Model 165	2219	2119
	STU	Model 165	2219	100
1957	B	Hummer	1350	1230
	ST	Model 165	2401	2051
	STU	Model 165	2401	350
1958	B	Hummer	1677	1684	Serial number 58 B 2684 reported
	ST	Model 165	2445	2201
	STU	Model 165	2445	244
1959	B	Hummer	1285	1390	See Note 2
	ST	Model 165	2311	1907	Serial number 59 ST 3326 reported Total ST/STU = 2326
	STU	Model 165	2311	419	Serial number 59 ST 3326 reported Total ST/STU = 2326
1960	BT	Super 10	2488	2169
1960	BTU	Super 10	2488	319
1961	BT	Super 10	1587	1280
1961	BTU	Super 10	1587	307
1962	BT	Pacer	1983	745	Serial number 62 BTH 4986 reported Total BT/BTU/BTH/BTF = 1986
	BTU	Pacer		62
	BTF	Ranger		186
	BTH	Scat		993
1963	BT	Pacer	575	581
	BTU	Pacer	50	50
	BTH	Scat	1125	1131
1964	BT	Pacer	600	600
	BTU	Pacer	50	50
	BTH	Scat	800	800
1965	BT	Pacer	500	500
	BTU	Pacer	50	50
	BTH	Scat	800	800
1966	BTH	Bobcat	1150	1150

Note 1: The 1954 STU was listed on the 1954 Dealer Order Blank, but no Club members reported any. The 1954 STU was either not popular or not readily available. We've listed 0,,but there probably were some produced.
Note 2: Club members reported 55 B 2338, 55 B 2354 and 55 B 2390 - all three above Harley's production figure. This is a big discrepancy, and it appears that Harley's figure was way off the mark.