This is not an article on pre-purchase-inspecting a BMW air-cooled twin motorcycle (aka Airhead, manufactured 1970 to 1995). Nor does this article contain information about how to prepare the motorcycle for sale. This is an article for a seller and purchaser about safety in negotiations and making a deal, test rides, handling a title, etc. The author’s website contains well over 100 articles on maintenance, but I do not necessarily expect you to read them prior to, for example, purchasing a motorcycle. If you are new to BMW Airhead motorcycles, I suggest you post an inquiry to the free Airheads LIST, for comments on things you should know about Airheads, and if you have a specific model (and perhaps year), or specific questions, that LIST is THE place for inquiries. Different years and models have specific things to know and be aware of. You may join the LIST here: http://lists.micapeak.com/mailman/listinfo/airheads
This article contains a large amount of information regarding vehicle numbers and identifications, most especially for BMW Airhead motorcycles, but much of this information also applies to other motorcycles, and even your automobile, truck, etc. Information may seem confusing at first. You are advised to slowly read this entire article, and then re-read; and then look at the numbers on your own bike(s), car, truck, etc.
You may be interested in the information in: https://bmwmotorcycletech.info/models.htm and https://bmwmotorcycletech.info/transmission.htm. Those two articles have some further identification information.
There is a LOT of wordy reading here …but, it can be important!
BMW may use different frame and motorcycle identification systems for non-U.S.A. motorcycles. There may be a letter or two letters, followed by a serial number. There may be a serial number followed by one extra number, and then the type of motorcycle. Seven (7) digits are used for the serial number. I do not know what the letters nor the 8th digit means, it could be a check-digit. The VIN system of 17 characters may be absent, in favor of just the Serial Number, with possibly a very small BMW roundel stamping and a letter or two or other number or two. This has especially been seen in later Airheads for ECE shipments. In general, the 17 character VIN system was introduced in approximately 1980-1981.
(1) This article’s information was gathered from quite a number of sources, places and publications; but especially from several old factory (German literature) publications. It is believed mostly, but not absolutely correct. BMW factory literature varies in production numbers and serial numbers for quite a few models. BMW has, at times, confused…and mixed-up…their own figures. This has been particularly so when BMW has used both reserved serial numbers range for a model; and, serial numbers for actual production. BMW vehicle numbers are the serialized number of the frame or engine or both, the more modern versions of which can be 6 or 7 digits, and can be seen on the engine, and/or frame. After ~1980, the numbers are usually the last 7 digits in the new 17 character VIN numbering system, but this is not universal for all Country’s shipped-to. From 1984, BMW stopped stamping serial numbers into the area next to the engine oil dipstick. There is a LOT more to all this. See (5) below; and, see my companion article: https://bmwmotorcycletech.info/IDnumbrs.htm.