I found some info but it's from 1981.
Manufacturers had been given notice about changes to VIN so it's probably relevant?
This is specific to Suzuki, I'll add to it as I find more info
The first digit of the frame number indicates the country of origin, in this case “
J” for Japan. Other numbers or letters used might be “
5” for units produced at Suzuki’s Rome, GA plant, “
K” for Korea, “
L” for Taiwan, or “
V” for France. Notice there really is no standard for determining what letter to use for what country. If the letter is unknown, check with a government agency.
The second digit indicates the company that made the unit, in this case “
S” for Suzuki. If the unit was made by a subsidiary, there might be another letter, such as “
M”
or “
T.”
The fourth digit, “
G” in the example shown, indicates the type and line as indicated in the chart below:
G = GS/GSX
The seventh digit, “
4” in the example shown, indicates the design sequence
The third through eighth digits provide information as to the type and model of the vehicle. Different manufacturers may use slightly different formats from each other, but must remain consistent within the company. In Suzuki’s format, “
1” used as the third digit indicates the vehicle is a motorcycle and “
A” indicates it is an ATV. Yamaha, by contrast, uses “
A” for motorcycle and “
4” to indicate a four wheeler. Hence
JS1…. would be Suzuki’s format, while
JYA…. would be the beginning of the VIN for a Yamaha motorcycle.