Original info from Biglry – taken from the VTX parts catalog

VIN #
We’ll use the VIN # from my 2002 1800 C as an example:
1HFSC46042A006692

WMI (World manufacturer identifier)
The first three digits of the VIN # are the WMI. This tells the make and type of vehicle.
Mine is 1HF

JH2 = Honda motorcycle (Manufactured In Japan)
1HF = Honda motorcycle (Manufactured in USA)
YC1 = Honda motorcycle (Manufactured in Belgium)
9C2 = Honda motorcycle (Manufactured in Brazil)
3H1 = Honda motorcycle (Manufactured in Mexico)
VTM = Honda motorcycle (Manufactured in Spain)
ZDC = Honda motorcycle (Manufactured in Italy)
JH3 = Honda all terrain vehicle (Manufactured in Japan)
478 = Honda all terrain vehicle (Manufactured in USA)

VDS (Vehicle Description code)
The next five digits are the VDS, this varies from Honda to Honda but for the VTX there are 2 options.
Mine is SC460

SC461 = VTX1800 CA
SC460 = VTX1800 49st

Check digit
The next digit is the check digit. This single digit is used to detect errors in the VIN and consists of a single digit number or letter (except I, O, Q, and U).
Mine is 4

model year
The next digit represents the model year.
Mine is 2

B = 1981
C = 1982
D = 1983
Y = 2000
1 = 2001
2 = 2002
3 = 2003
4 = 2004
etc…

Assembly plant
The next letter/number tells the plant the bike was built in.
Mine is A

A = Ohio factory in USA
B = Aalst factory in Belgium
C = Saitama factory in Japan
D = Guadalajara factory in Mexico
E = Montesa factory in Spain
F = Atessa factory in Italy
K = Kumamoto factory in Japan
M = Hamamatsu factory in Japan
R = Manaus factory in Brazil
S = Suzuka factory in Japan
T = Tochigi factory in Japan
4 = South Carolina factory in USA

VIS (Vehicle indicator section)
The last six digits are the sequential production numbers, also known as the Vehicle Indicator Section (VIS)
Mine is 006692 so I know based on my VIN# that it was the 6,692nd bike made at the Ohio plant in 2002

Any change or modification of parts is directly related to the VDS and VIS.
A VIS number will appear in the “serial #” column of the parts catalog if a part is changed or modified.