Motocross bikes that were manufactured after 1980 feature a 17-digit Vehicle Identification Number (VIN). The digits on the VIN represent the country of origin, manufacturer, details of the style, production number and a check digit to prevent vehicle identification fraud. Motorcycles made during or after 1981 will have the 17 digit VIN, but earlier models have a VIN of 11 to 17 digits. The VIN on a motorcycle can be found mounted on the frame.
Check the first digit of the VIN. This letter or number represents the country in which the bike was manufactured. For example, a bike made in Japan will have "J" for Japan, and a motorcycle made in the U.S. will have a "1," a "4" or a "5". The second letter of the VIN represents the manufacturer. For Suzuki, for example, this is an "S." Check the third digit of the VIN; this represents the type of vehicle, and for a motorcycle, this should be a 1.
Look at the next five digits as a section. This is the vehicle descriptor section. This will tell you the vehicle category, piston displacement or size, engine type, design sequence and model variation. For off-roaders, the first digit will be an "S," and for bikes under the single-cylinder sport-street category, this will be an "N." Multiple-cylinder sport-street motorcycles fall under the designation "G." The next digit will be a letter representing the size of the engine. For example, a Suzuki RM85 will have a "D" because the engine displacement is in the 80 to 89cc range. The RM85 is a two-stroke, single-cylinder bike so the next digit will be a 1. The next two digits stand for the design sequence (model version) and the model variations, so they will depend on the age and whether this particular bike is a base model. The seventh digit could be a "1" for example, for the first model version of that bike. Base motorcycle models, such as the 2010 Triumph Tiger, generally use "A" for the eighth digit, whereas the 2010 Triumph Tiger Special Edition, with altered colour-scheme, would have a "B" or other letter in the eighth digit place.
Treat the ninth digit as a separate section. The ninth digit is a check number -- using numbers from 1 to 9 and the letter X -- that manufacturers use to prevent vehicle identification fraud. The check digit is calculated using an algorithm made up of the other digits in the VIN.
Look at the 10th digit. This will tell what year the bike was made. Motorcycles made before 2001 have letters for identifying years. From 2001 onwards, numbers are used. For example, a 2003 bike will have the number "3" in the tenth VIN place. The 11th digit identifies the plant where the bike was made.
Find the 12th to 17th digits. These are the production sequence identifiers that allow the manufacturer to pinpoint at what time the bike came off the production line. These will be specific to individual bikes.