meaning of /2, /3, /5, /6, /7?

The BMW Airhead motorcycle /2, /3, /5, /6 and /7 models, what do they mean?

by Duane Ausherman

For some years and still in 2018, this page is my most popular one and I am shocked. 

BMW changed their motorcycle designation system so often over the years that it is very confusing.  This is an attempt to clarify it a bit.  The slash (/) followed by a number does have a generally accepted meaning.  BMW may not agree with it, but who cares what they think?   It is often a “rubber” meaning in that it sort of stretches to fit.  BMW assigned them and owners and collectors have altered them to sort of “fit” the way we see them.  I will try to avoid a repeat of detailed BMW history and just give some of the current thinking and models vs. years.  The years are not exact, as BMW sold different models in various countries.  BMW has tended to change significant things without a model change.  Please don’t bug me with your exceptions, as there are plenty of them.  This information is general.  This will give a normal person a headache, so get the aspirin ready.

The /3 BMW, 1951-55

After war WWII, BMW was in dire financial straits.  They sort of pulled parts out of the rubble and sold whatever they could to get some cash.  There certainly was no money for designing and testing new models etc.  The single cylinder R24 was almost a copy of the pre-war R23.  In 1950 the allied powers relaxed the regulations on Germany and permitted a 500 cc (cubic centimeters displacement) to be produced.  It was the R51/2, but it was really a pre-war design.  So is that a /2?  Yes, but only literally and not according to the popular “/2” designation accepted by most.  In 1951, BMW came out with a new model, the R51/3.  That started the /3 model designation.  They also had a 600 cc version called the R67, with no slash at all.  Not many were made and it is rather rare.  The next year they altered it a bit and called it the R67/2.  Is this a /2?  No, it is a /3 but was made in large numbers.  The R67/3 was made in small numbers and fairly rare.

In the single cylinder line BMW came out with the R25, no slash, in 1950 and it is a /3 too.  Then the next model was the R25/2, in 1951, and it is a /3 also.  Finally, they came out with the R25/3.  In 54 they came out with the R67/3 and it was built in small numbers too.    See the problem?

The breakdown of the /3 models.

R25, R25/2, R25/3, a 250 cc economy bike.

R51/3, a 500 cc low tuned bike

R67, R67/2, R67/3, 600 ccs, low tuned bikes for a sidecar.

R68, a 600 cc sportbike.  This is the one to have.

The /2 BMW, late 55-69

Now we are stepping into really confusing territory with the /2.  In late 55, BMW introduced a series with a different fork and frame.  They were the R26, R50, R60, and R69.  Meanwhile, they were still selling some of the /3.  I have one brochure showing both the new (/2) and the old (/3) series for sale.  The distinctive change was the forks.  They used a fork designed by a Brit named Earle and so they were Earle’s forks.  It was the best fork for a sidecar bike.  Both singles and twins used it.  As could be expected, these newly designed bikes had some design defects.  They were corrected in mid 57, but not assigned any new model number.  This change was called the “Accessory Group” and widely advertised.   It was actually a larger change than in 61 when they added the /2.

For 1961, BMW upgraded the engines slightly and added the /2 designation.  They were the R27, R50/2, R60/2, and the R69S.  So, BMW would say that these are the /2 models.  For some reason, owners also started calling the previous 5 years of production the /2.  It makes sense because they were virtually the same.  Most parts were interchangeable, at least in one direction.  It must be kept in mind that often BMW would change some significant part and tell nobody.  It would show up a year later in parts books, or maybe not.  If it was a direct interchange in both directions, no mention was made anywhere, including the parts book.

BMW sales eventually slumped with this sidecar fork and low-performance bike.  They began designing a new model in the mid-60s.  They were going back to telescopic forks and needed to test them.  In 1968 they began fitting some models with telescopic forks.  By 1969 almost no Earles forks models were available.  The ones with the new forks got called US models with no slash.  The bikes with the telescopic forks are R50US, R60US, and The R69US.  They are still a /2.

From 1961 through 1967

R27, a 250 cc single, ceased factory production in 1966.  Official importation stopped in the USA in 65, but a few were still on dealers floors for a couple years and the title could show anything.

R50/2, a 500 cc low tuned bike

R60/2 a 600 cc low tuned bike and generally considered to be for sidecar use by the factory, but few in the USA were.

R50S, a sport 500 cc bike, ceased in 63, not successful

R69S, a 600 cc sports bike, very successful and the one to have

1968 and 69, the new suffix “US”

R50US, R60US, and the R69US, generally the same, but with telescopic forks.  In the USA we started getting them around March 1968, but only a few.  By mid 69 almost all new bikes came with the telescopic forks.  These models we still know as a /2.

The /5 BMW Motorcycle

The new models were the /5 series and a great improvement over earlier years in both performance and reliability.  Some reliability and production problems occurred and changes were made.  These are well documented elsewhere on this site.  The largest was changing from a short wheelbase (SWB) to a long wheelbase (LWB) in early 73 with no change in designation or any real notice to buyers.  BMW had added about 2″ to the swing arm.

The story of how my factory visit caused the change from the SWB to LWB is here.  Go about 2/3 the way down and start reading the section titled “The wobble issue.”  You will learn how Butler and Smith treated dealers and how the wobble issue was more or less fixed by BMW.

The /5 years, 70-73, is as long as BMW ever produced bikes without a specially designated sportbike model.  Ironically, BMW only kept a few parts from the /2 series.  One of them was a joke and never did work well the fuel petcock.  It leaked from the beginning.  That is another story.

Here is the breakdown of models for the years 1970-1973.

R50/5, a 500 cc bike

R60/5, a 600 cc bike

R75/5, a 750 cc bike, the one to have

The /6 BMW

BMW released a new model in 1974 called the /6.  The 600 cc model still had a drum, some a single and one, a double disc brake, all had a larger battery and a 5-speed transmission with a kick starter that didn’t work.  They dropped the useless kick starter for 1975 in the USA delivered bikes.  A sports model (900 ccs) was introduced called the R90S.  It has become a favorite of collectors and riders alike.  Even though the R90S didn’t use the /6 designation, it is /6.

R60/6, with drum front brake

R75/6, with single disc brake

R90/6, with single disc brake

R90S, with double disc brake and a bikini fairing for the sports look. this may be the one to have

The /7 BMW

It starts to get interesting in 77.  While a few R60/7s came into the country, it was very few.  The 750 cc was increased to 800 ccs after only one year as a /7.  BMW was now using other designations for models, even though they were of the /7 series.  Even though the “S”, “RS” and the “RT” didn’t use the /7 designations, they were /7s after all.

R60/7

R75/7, 1977 only

R80/7, starting in 1978

R100/7, touring model, very basic

R100S, with the cafe, or bikini fairing

R100RS, (Renn Sport) with the small cockpit fairing

R100RT, with a larger fairing and upright seating position

In 1979 BMW came out with a newly designed 450cc/650 cc called the R45/R65 and a whole lot of designations that never again included a /.  The R45 was not available in the USA.  We often called them the “little twins”.  Even though none used the /7 designation, the big twins were really a /7.  Is that confusing enough?

To learn about the newer models after 1981, you will have to go elsewhere.  I have no idea what they are.  I have never even ridden any of them.

BMWmodel.GIF (113590 bytes)

Models, by year, with VINs

Another aspect of the BMW motorcycle model designations

On the slash 2 Yahoo list, the question was asked, “Was there ever a /4 made?”

This is my answer, “There was never a /4 produced and called that.  When I imported /2 Nural pistons direct, many of the boxes said /4.

Mark Hugget, the head of Mobile Traditions commented (cut and pasted).

This is a common error by suppliers from BMW.  The suppliers such as Nural; KS or Mahle receive a technical drawing and a purchase order with the BMW internal technical drawing number eg.  267.1.03.610.03 which is a piston for an R67 to R67/3.  The changes and thereby new items for the R60 motor which were derivatives of 267.1….  parts, received the identification 267.4….  Thereby, the R60 piston had the technical drawing number 267.4.03.610.03.  The BMW suppliers miss-interpret this information and sell the pistons themselves for a so-called BMW R67/4 (Which is an R60).  Likewise, the R60-2 piston has the drawing number 267.5.03.610.03.  On the same line, did you know that an R69S is indeed an R68/3????  Now you are confused!

Since BMW made a very confusing mess of their own system, I think that the “unofficial” system is more useful.