Home > BRAP Blog > Harley-Davidson History and Reference Guide > Harley-Davidson Model Numbers Explained
There have been some exceptions and variations in the Harley-Davidson model number system throughout the years, but this guide covers the general idea for the most part.

1937 - Present
The first letter block typically designates the engine series:
Letter(s) Designation
E Big Twin 61 ci, overhead valve, with separated engine and transmission
F Big Twin 74, 80, and 88 ci, overhead valve
G Servi-car three wheeler
K 45 and 55 ci, side valve that replaced the W
U Big Twin 74, and 80 ci, side valve
V 74 ci, side valve as well as 1130 cc and 1250 cc Revolution Engine
W 45 ci, side valve
X EVO 883 and 1200 cc engines

The second letter block typically designates the frame size:
Letter(s)Designation
LLarge frame
XSmall frame

The third letter block typically designates the suspension:

Letter(s)Designation
DLight framed swing arm suspension
STBoth light and heavy soft tail suspension
HHeavy suspension

The fourth letter block typically designates the model:

The fifth letter block typically designates the specific options:


1916 - 1936
In 1916 the model numbers switched from the sequential order they had been following (Model 11 in 1915) to the last two digits of the production year, but continued to use letters to indicate various options. In 1930 they started separating the model number and Option code with a hyphen but the idea remained the same.

Example:

Model Number Year Engine Options
16C 1916 35ci F-Head single cylinder magneto ignition, 3 speed, chain driven
30-DL 1930 45ci V-Twin, Side Valve High Compression

1904 - 1915
From 1904 through 1915 with a few exceptions in 1912 and 1915 the model number was a sequential number starting with 0. In 1909 letters began to be added to the end of the model number to indicate options, such as engine, ignition, wheel size, etc.

Example:
Model Number Year Engine Options
4 1908 26.8ci F-Head single cylinder
5A 1909 30ci F-Head single cylinder magneto ignition, 28in wheels


1903
As far as we are aware there was no designated model number for 24.74 ci F-Head single piston bikes and only three were made.