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/2 BMW motorcycle restorers details

by Duane Ausherman


This page is about the models from the early 50's to the late 60's.  Including the R25, R25/2, R25/3, R51/2, 51/3, R67, R67/2, R67/3, R68, R26, R50, R60, R69, R27, R50/2, R60/2, R50S, R69S, R50US, R60/US and the R69US.  You may find some useful info here.  

Once I had in my head a lot of old BMW detail information, but it is mostly gone now.  I was able to document some of this info during a visit with Chuck, a BMW restorer.  Consider this to be a guide and neither complete nor exactly accurate.  I will give my impressions of the era and hope that you, the reader, will be able to offer more accurate info that can be included here. 

Wheels and Hubs

Wheel building article, by Lonnie Walker

The wheels for the single cylinder models (R26 & R27) had only 36 spokes and the twins had 40 spoke wheels.  Only two hubs were offered for the production of the twin cylinder Earles fork models.  There may have been many different casting changes due to a change in technology, but only two that affected the spoke pattern.  The first ones had 3.5 mm (actual .120") spokes that crossed each other near the hub.  The later ones (from mid 57 on) had 4 mm (actual .136") spokes that crossed each other in the middle.  The early ones were too small (weak) and a very poor pattern for sidecar forces and so were "beefed up" a bit.  

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The early pattern.  See how the spokes cross very near the hub?

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The later pattern.  See how the spokes cross almost in the middle? The spokes must not touch where they cross.  If they touch and seem to "bend around" each other then the rim is laced up backwards or the rim isn't an original type.  Some are out that sort of work, but are Italian and are not a match. 

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This is the early hub used up till mid 57, showing the details so that one can identify a bare hub.  I have shown it with a US quarter.  For our foreign visitors that coin is 24.2 mm in diameter.  Here you can see that a larger coin would fit the curve much better.  The recess into the hub for the spokes is rather shallow. 

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This is the later hub used after mid 57, showing that the quarter fits very well into the hub recess.  Sorry about the poor lighting. 

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This rim is on a /3, but the paint scheme is identical to painted rims through the /2 series.  They were never imported into the USA, but were common in the rest of the world. 

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The Fulda tire was common in Europe, but was not imported into the USA as far as I know.  It was common during the 50s. 

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This shows the tread design of the Fulda tire. 

The R69 BMW "third muffler"

The R69 had a third muffler that was mounted under the motorcycle in place of the crossover.  As far as I know it was used throughout the production of the R69.  I have no idea what the idea was for including it.  Almost everyone just did away with it when it finally rusted out and used the usual crossover pipe, as on the other models. 

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The distortion of the lens makes it hard to see that it is exactly 9" long.  This is a NOS muffler and I think the only new one that I have seen since my first R69 back in 1963. 

BMW headlight lens and rim details

Bosch and Hella were the major suppliers for all lighting on nearly all central European cars and motorcycles in the 50s and 60s.  A lens from one motorcycle would fit many brands.  After market accessories were common place.  Here is an example. 

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The item on the top is an adjuster for the lens.  This is made by Hella and is NOS.  This is the first one that I can remember seeing.   

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The backside of the "adjustable" headlight by Hella. 

Hella also made a rim that we called the "eyebrow" rim.  The top of it stuck out over the headlight lens about 1/2" or so.  It was imported into the USA by Dixie International in Columbus, Ohio.  They sold very well, partly because they were slightly cheaper than the stock one from BMW dealers and because they were different.  If someone would forward me a picture I would add it here and give you credit.  

Glass lens

Most headlight lens used by BMW were from Bosch.  After the war and up till the /5 series, that lens was in several varieties.  Bosch had several suppliers and one could find small differences.  All were interchangeable.  I don't suggest that you will find all versions here, but you can see the main ones.  My time line is only my guess from my dim memory.  My photography is poor, but I tried different backgrounds to show the features. 

lens1.jpg (40220 bytes)

The oldest type, maybe used in the early 50s.  Look from about 10 O'clock and down around the lower edge and up to about 2 O'clock.  See the prominent U shape to the glass? That was even more obvious before WWII.  At time went along it diminished.  The area around the inner circle is of interest here.  The lower half has a patina to it.  It is sort of hazy or unclear.  This one has a lot of haze. 

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This one has much less haze, but is otherwise about identical. 

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This one has no haze and was used up until about the late 50s.  Consider the inner circle and the upper half of the outer circle area.  If you look very closely, you can see that every forth vertical line is larger and more pronounced.  If you held it in your hands it is more obvious. 

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This one was used from the early 60s on.  The photo shows the change in lettering away from the italics type.  The lettering is block type.  This was used up to the end of the /2 production. 

Bosch headlight rims

These came in several varieties too.  It was very hard to get the details in the photos, but I did my best.  In general, Bosch had an inscription of their name showing at the top center of the rim up till about 1962.  I think that the early inscription was lager than the later one.  The photo showing that difference in size didn't show the detail well enough and was omitted.  From about 62 on, it was a plain bare rim. 

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Typical inscription on the top.  I can't tell if this is the large one or the small one, sorry.  The difference is only obvious when you have both in your hand. 

BMW motorcycle valve covers

The valve covers came in three general types of construction.  They came in two styles, R50/R60 with 6 ribs and the sport type with two ribs.  All of one style were interchangeable except the R50S.   

1.  The first series was very thick, heavy and had distinguishing flashing marks.  These marks are from the poor quality molding process.  I suspect that they were sand molds.  They were used up until about 1961 or 62.   

2.  The second was also thick and heavy, but had no flashing marks.  They were used up until about late 1967 or 68.   

3.  The third were thin, light and made by a different process, maybe die cast.  The surface finish was smoother too.  They were available for many years after the /2 ceased production.  Someone that knows about sand casting and die casting please let me know so I can use the correct wording.  If the bike fell over, it was almost sure to punch a hole in the "thin" cover.  The older thick ones would withstand lots of falling over. 

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This R69 valve cover has the early flashing marks very visible.  They are the marks that extend out from the usual fins to the edge.  The R50/R60 valve covers also had the flashing marks. 

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This R69 valve cover has been "cleaned up" to get rid of the flashing marks.  This was a common practice.  It is too bad as it ruins the "original" value for restoration work. 

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This shows a R69 valve cover on the left and a R50S valve cover on the right.  The R50S never had the flashing marks due to being produced after the flashing marks went away.  The R50S covers are very hard to find today.  I have heard that a large supply of them turned up in Sacramento about 10 years ago, but I have no idea what the story is. 

Are all /2 BMW motorcycle transmissions the same?

The technical aspects of all twin transmission are the same.  They have the same gear ratios for all solo bikes.  They are almost completely interchangeable.  In this case, one must lump them into two groups.  The later sport models, R50S and R69S, used a different air cleaner.  That air cleaner was more open and allowed a bit more flow.  The R50, R60, R69, R50/2, and R60/2 used an air cleaner that had a choke lever.  Both types of air cleaner mounted in the same way, by a long bolt through the middle.  The choke type air cleaner was kept oriented by a roll pin that was mounted into the transmission case.  It must be removed to mount the sport type air cleaner. 

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Slightly below the center of the picture is the locating roll pin for the choke type air cleaner. 

/2 boxer twin BMW motorcycle air cleaner

The air cleaners for the twins with Earles forks can be divided in two types; one with a choke lever and the one without.  More than one manufacturer make them and so some small differences exist.  The choke type was used on all models up to the /2 in 1961.  At that time the two sport models, R69S and R50S, were provided an air cleaner without the choke ability.  The advantage is that the new unit allowed more flow of air.  In 1968 with the advent of the telescopic forks, all models lost the choke lever air cleaner. 

Choke or lever type air cleaner        


The choke lever often gets rusted and won't budge.  Soak it in your favorite oil, maybe WD-40 for a few days.  It will eventually move.  The choke has a detent in it to keep it in the open position. 

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A side view of the /2 BMW motorcycle choke type air cleaner with the choke lever open or off. 

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A top view of the R50, R60, R69, R50/2, R60/2 BMW choke type air cleaner

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The two parts of this air cleaner often become rusted together.  Soak the joint with oil for a few days.  Turn the air cleaner upside down.  For a tool, I use the wheel bearing 4" spacer made from a 3/4" water pipe nipple.  I put it on over the long bolt and hold the lever part (upper portion) and hit the spacer with a rubber mallet.  That has never failed to separate the two parts. 

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The two parts separated

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The "O" ring at the bottom to seal the element from leaking

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The same "O" ring at the top to seal the element from leaking

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The "O" ring

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This shows the snap ring that keeps the mounting bolt from getting lost. 

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This is the label that was on the elements

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This shows the element

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Just above the "O" ring is a dimple in the sheet metal.  It is at 12 O'clock.  That is the detent to keep the choke lever from "creeping" to the choked position. 

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This shows the choke in the 1/2 way position

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The gasket for all air cleaners.  The hole that is visible at 6 O'clock is the hole that mounts over the roll pin on the top of the transmission.  The transmissions for the sport models didn't have this pin.  That is the only difference in the transmissions of the years from 61-67.  The roll pin can be removed easily and installed in another transmission. 

The sport air cleaner for the BMW motorcycles R50S, R69S and all of the US models. 

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In this photo, one can see the slightly bent inside rim of the bottom plate of the air cleaner.  That bent part is to locate the air cleaner and keep it from rotating on the transmission.  This one is less bent that is proper.  The bends get mangled due to improper mounting of the air cleaner.  Improperly mounted air cleaners on the sport models will always cause the tuning to be a bit different. 

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The little "dents" in the front of the air cleaner to align the top and bottom. 

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This shows the top of the sport type air cleaner elements.  It has a solid metal end.  Many have mounted this filter upside down and that effectively blocks all air from going into the carbs.  The bike will start easily, but not run above 2000 rpm.  Later elements had this part open so that it could be mounted either way. 

Original metal cable and wire ties

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These are original NOS cable ties.  They would rust up the frame where they touched.  For a restoration, I suggest using modern black wire ties used in electronics.  For judging at a serious show, just remove the plastic and "gently" install the proper metal ones.  After the show replace the metal ties with the plastic ones.  By not sharply bending the metal ones, they can be reused many times. 

The VDO clock

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This is a very rare accessory that you will probably never see. 

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This page was last edited: 04/08/2006 - copyright Duane Ausherman
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