Yamaha has produced many years' worth of the YZ80 off-road motorcycle. However, the style didn't change much, so it's difficult to tell them apart. All YZ80s made after 1980 have manufacturing information in the Vehicle Identification Number (VIN). Finding the year on the VIN is straightforward, but for other VIN detail, you will need to use a VIN decoder.
Find the VIN on the YZ80, which will be stamped on the frame or on the engine casing. For bikes built after 1980, the VIN has 17 characters. For bikes manufactured before 1981, the VIN could be 11 to 17 character and is much harder to decode than the newer VIN.
Clean off the VIN so you don't make a mistake in transcribing it. If the VIN is worn, make a pencil and paper rubbing to pick up the characters. If the code is not 17 characters, it could be another manufacturer's code or the bike could have been built before 1980.
Look at the 10th position of the VIN code. The tenth character stands for a particular year. From 1980 to the year 2000, the character is a letter. The sequence begins with A for 1980 and continues through to Y for 2000, skipping the letters O, Q, and I (which are never used anywhere in a VIN), and the characters Z, U and zero (which are never used in the year code). From 2001 until 2009, numbers from one to nine are used. In 2010, the code resets to the alphabetic sequence beginning with A.
So for example, a 2004 YZ80 will have the number four in the tenth position, and a bike built in 1985 will have the letter F in the tenth position.
Enter the YZ80 VIN into the Yamaha VIN decoder at motoverse.com, and you can get a detailed breakdown of the motorbike, including confirmation of the year code. The VIN decoder will also tell you the country of manufacture -- "J" for Japan, for example -- in position one. The second character stands for the manufacturer. The next five characters denote the details of the bike and the ninth character is a check digit for anti-fraud purposes. The eleventh character denotes the plant of manufacture and the remaining group of six characters tells you the production sequence of the bike in the plant.
For older VINs, calling Yamaha customer service at 800-962-7926.