Restorers details

/2 BMW motorcycle restorers details

by Duane Ausherman

This page is about the models from the early ’50s to the late ’60s.  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.

I once had a lot of old BMW detail information in my head, 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.

When you see “mid 57”, Which means the first couple of years of production, many defects were corrected and released in the marketing known as the “accessory group.”   These changes (fixes) were more important than the changes in late 1960 when BMW denoted it with the added suffix, /2.

Changes were common over the next several years, the largest being in 1968-69 with telescopic forks, replacing the Earles forks.  Those are called the US models.

Wheels and Hubs

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 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 had 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 double cross 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 backward, or the rim isn’t an original type.

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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 size comparison.  For our foreign visitors, that coin is 24.2 mm in diameter.  Here, 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 with this paint scheme 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 “third muffler.”

The R69 had a third muffler that was mounted below the transmission and in place of the crossover.  As far as I know, it was used throughout the production of the R69.  I have no idea why it was used.  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 in 1963.

BMW headlight lens and rim details

Bosch and Hella were the major suppliers of all lighting on nearly all central European cars and motorcycles in the 50s and 60s.  A lens from one motorcycle would fit many brands.  Aftermarket accessories were commonplace.  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 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.

Glass lens

Most headlight lenses 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 the versions here, only the main ones.  My timeline is only my guess from my dim memory.  My photography is poor, but I tried different backgrounds to show the features.

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The oldest type may have been 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 on the glass?  That was even more obvious before WWII.  As time went along, it diminished.  The area around the inner circle is of interest here.  The lower half has an intentional 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 fourth vertical line is larger and more pronounced.  If you held it in your hands, it is obvious.

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

Bosch headlight rims

These came in several varieties.  In general, Bosch had their name inscribed at the top center of the rim until about 1962.  I think that the early inscription was larger 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.  Sorry, I can’t tell if this is the large one or the small one.  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 sports type with two ribs.  All were interchangeable except the R50S, as it was unique to that one model.

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 was 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.  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 stress.

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This R69 valve cover has early flashing marks visible.  They are marks extending from the usual fins to the edge.  The R50/R60 valve covers also had these same 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 restoration work’s “original” value.

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This shows an R69 valve cover on the left and an R50S valve cover on the right.  The R50S never had the flashing marks due to being produced after the flashing marks went away on other models.  The R50S valve covers are hard to find.

Are all /2 BMW motorcycle transmissions the same?

The basic technical aspects of all twin transmissions are the same.  They have the same gear ratios for all solo bikes and a different ratio for sidecar transmissions.  They are almost completely interchangeable.  In this case, one must lump them into two groups.  First, the later sports models, R50S, and R69S, as they used a different air cleaner.  That air cleaner was more open and allowed a bit more flow.  Secondly, the R50, R60, R69, R50/2, and R60/2 used an air cleaner that had a hand-operated choke lever.  Both types of air cleaner are 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 in the transmission case.  It must be removed to mount the sports-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 into two types, one with a choke lever and the one without.  More than one manufacturer made them, so some small differences exist.  The choke type was used on all models up to the /2 in 1961.  At that time, the two sports models, R69S and R50S, were provided with 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 for a few days, and it will eventually move.

The air cleaner used up until mid-57 had the top piece with a square edge, not the rounded one shown just below.

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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, and 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.  I use the wheel bearing 4″ spacer made from a 3/4″ water pipe nipple for a tool.  I put it on over the long bolt, 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 seals 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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A dimple in the sheet metal is just above the “O” ring.  It is at 12 O’clock.  That detent keeps 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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This is the gasket for all air cleaners.  The hole that is visible at 6 O’clock in the hole that mounts over the roll pin on the top of the transmission.  The transmissions for the sports 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.

The sports air cleaner for the R50S, R69S, and 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 than is proper.  The bends get mangled due to improper mounting of the air cleaner.  Improperly mounted air cleaners on the sports models will always cause the tuning to be a bit different.  Fix it.

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The little “dents” in the front of the air cleaner align the top and bottom.

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This shows the top of an early sports type air cleaner element.  It has a solid metal end.  Many have mounted this element 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, remove the plastic and “gently” install the proper metal ones.  After the show, replace the metal ties with plastic ones.  They can be reused many times by not sharply bending the metal ones.

The VDO clock

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This is a very rare accessory that you may never see.

Earles fork models from late 1955 to mid 57

This page is mostly about the BMW motorcycle models R26, R50, R60, and the famous R69 from the start (late 55) to mid 57.

The Earles forks were mentioned in the owner’s manual in 1954, so they had already been tested and approved for production.  I suspect that BMW was so pleased with the new fork that they just couldn’t resist whetting the apatite of potential buyers.  They were specifically called constant wheelbase forks for sidecar use.  They were introduced in 55 in Europe and in late 55 in America.  Not all models were available with Earles forks from the start.  BMW was selling off old stock before releasing all of the new Earles fork models.

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This is a sales brochure in English that promotes R25/3, R50, R69, and R67/3.  The print date is 1/55.

Weaknesses appeared in the new models, and changes followed in mid-57.  The 56 to mid-57 BMW twins are quite different from the mid-57 and later ones.  BMW’s advertisements called the changes (read “fixes”) the “accessory group.”  Here is what I remember of the changes.

1.  The biggest is the transmission.  All bikes had been equipped with sidecar gearing as standard.  The solo gearing was optional, except maybe in the R69.  The sidecar transmission has no mark on it with the “S,” meaning “solo.” The mark is found in two places.  One is just in front of the drive for the speedometer.  The sidecar transmission will have no “S” on that horizontal flat place.  The bike should only go up to about 15 mph in first gear, and then you must shift.  If you must shift out of first by 15 mph, then you have the sidecar gearing.  In mid 57, all twin models had the solo gearing marked “S” for Sport.  From the first models in 56, the sports gearing was an option.  Starting in mid 57, the sidecar gearing was an option.  The first picture below shows nothing in the horizontal flat spot.  The later sports transmission was marked with an “S” in two places, at the oil filler plug and the speedometer drive.  They can be seen in the middle and right photos.

     Sidecar transmission                    Sport transmission

 Sport transmission

How does one know what the ratio is if the bike can’t be ridden?  Easy, measure the number of rotations in first gear.  Carefully shift the transmission into first gear.  Make a mark on the top of the input shaft and output shaft flange.  I use a magic marker.  Carefully rotate the input shaft and count the turns to get the output flange to go around once.  The sidecar transmission will take 5.3 turns, and the sports transmission will take only 3.7 turns.  If the transmission is still in the bike, then mark the flywheel and count the revolutions.  Peel back the driveshaft boot and count the revolutions of the output shaft.

2.  The speedometer is marked with shifting points for the wide ratio sidecar gearing.  That was changed in the accessory group to the sports type spacing.

3.  The spoke pattern for the wheels is different.  The older wheel’s spokes cross each other near the hub, not in the middle of the spokes, as in the later version.  The spokes are smaller in diameter, 3.5 mm, not the later, and stronger, 4 mm.  The spoke called 3.5 mm measures .120,” and the 4 mm spoke is .136″.  The hub, rim, and nipples are, of course, different too.  The wheel bearing system is the same.

The two spoke patterns are known differently.  The early type has the spokes crossing in only one place and is called the “one cross.”  The post-mid-57 type has the spokes crossing in two places and is called the “two cross.

The older spoke pattern.

4.  BMW increased the battery size for bikes imported into the USA.  The older battery is very small and is almost square.  It is 90 X 80 X 162 mm high.  The box, or holder, is also small.  The battery strap is shorter too.  Forget ever finding one of those.  A larger battery was added to these models.  Generally, we didn’t change the battery holder to change the battery to the larger one.  We just bent the locating tabs flat.  You can bend them back up if you find one that has that mod.  This larger battery was for the USA, and all the bikes that I saw from Europe still had the smaller battery until at least up to 1968.  It was 120 X 90 X 165 mm high.

5.  The older headlight ears are smaller, and they break easily, and most have been replaced with the newer, wider ones.  The difference is where the ear widens to meet the part bolted to the fork down tube.  The later one is about 3.5 ” wide, and the earlier one is about 2 3/4 ” wide.  The narrow one cracked vertically at the place right behind the 14 mm chrome bolt that holds the headlight, just where it starts to widen out.

This is the early one.

6.  BMW increased the leverage on the rear brake shoes.  On the final drive is the vertical brake arm that holds the long adjustable rod.  The correct older one is very short, about 1.25″ center to center, of the shafts.  The later one is about 2.10″ center to center.  The change was made to get more power to the brakes.  The short ones were painted black, and the longer ones were cad plated.  The early brake rod was also painted black.  These comments about color and finish are only for bikes imported into the USA by the distributor.

The short brake arm.

7.  The older front fender has only two mounting points, front and rear.  The later fenders have a midpoint mount, which is a flat brace mounted just behind the shocks.  This fender, when removed, has no brace on it at all. The later fender has the brace riveted to it.  This braceless fender was also used on the R26 and R27 until the end of production in 66.  A bit odd that the fenders without the brace were used on the two models that vibrated the most.

8.  They continued using the very small tail light that had been used since the late 30s.  The small tail lights were supplied by a variety of firms and were slightly different.  It was replaced by the one that we know so well as /2 “coffee can.” The small light has a glass lens.  The larger coffee can lens is plastic.

9.  Some of the bikes that were equipped with solo seats had a coil spring and not the commonly known rubber “silent block.”  This spring was abandoned very quickly, well before the mid-57 “Accessory group” changes.  This seat is very rare, and I have only seen three of them.

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Other changes, but not limited to those early models

Not part of that series change called the “Accessory Group” were a few other things you must have to be correct.  These items were used until they ran out of them.

1.  The little half-moon cover that hides the small air cleaner for the air that is drawn on over the engine electrics is held on by a fancy knurled nut of about 1″ in diameter.  This small round filter was used up until 1968 when BMW just deleted it, probably to save money.

2.  They were still using the older style of headlight shell from the R25/3 single.  It had a 3-4 ” big round “dent” in the rear of it.  It was hard to see as it was at the lower rear and was for clearance of the R25/3 horn.  They just “used them up” and then began using the ones without the dent.  I can’t say for sure when they changed that part, but the old ones all had the dent. The ones with the dent were available as spare parts for some time.  I bought 20 of them at “close out” from Bosch in 1968.  I used them whenever a customer needed a new shell.  This has caused some confusion as to what is “correct.”

3.  The pre-1961 headlight glass had a big “U” cast in it.  The older (back into the 20s) the BMW is, the more pronounced the “U.”  The “U” is seen around, the lower part only about 1/2″ in from the edge.  The upper parts of the “U” terminate at about 10 and 2 O’clock.  The lower 40% of the glass has a mottled look or patina cast into the glass.

4.  The Bosch motorcycle headlight rim has the manufacturer’s name on the top, in plain sight, “Bosch D’Allemagne” or something similar.

5.  It should have the heavy horn, not the later “lightweight” one.  I don’t remember the year of that change.

6.  There should be no 13 mm fasteners anywhere on the bike, only 14 mm.  The first 13 mm fasteners showed up in late 63, and by 65, no 14 mm were being used on the exterior.  In 1964, they used up the remaining stock of 14 mm.  The 64-year model could have both 14 mm, and 13 mm fasteners.

7.  The carbs must have a small diameter outside float chambers.  BMW changed to the carbs with the larger chambers in 63 to accommodate a sidecar rig going through a very long curve.

8.  The very early air cleaners were more square than those later.  The air cleaner comes apart to access the filter element.  The upper part has a square corner and later is quite rounded off.

9.  The early final drives had no venting system.  In 63, BMW added a vent or breather to the top of the housing.

This final drive is on a 56 BMW R69.

10.  The early flywheels had a pressed-in ball bearing for the timing marks.  Around 1959 they went to stamped in marks.

The early BMW motorcycles used a ball bearing pressed into a hole in the flywheel for the ignition timing marks.

See the shiny ball?  Those were found up until around the late 50s on all models.  They were on the /3 models too.  Please let me know if you have proof of the beginning or end dates.  Photo by Thomas Browne, thanks

The early headlight shell

The R25/3 had the horn mounted just behind and below the center of the headlight shell.  The shell was “dished in” or “dented in” to make more room.  The dent is about 4″ (10 cm) in diameter.  BMW used this shell for the next few years on all models that I know of.  I do not know when they finally ran out of them, but I would guess about 58-60.  They were available as spare parts for even longer than they were used in production.  Some dealers still had them on the shelf years later.  In 1968 I got 20 of them from Bosch in Canada very cheaply.  Since the shell is black, it is hard to photograph.

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Side view of the dish or dent.  Photo by Tomas Melander, thanks

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This headlight is mounted on my R25/3.

BMW motorcycle spark plug caps

1.  This is the stock cap used from the mid ’50s to about 74.

2.  The plug cap screws onto the plug wire.

3.  The resistance is stamped into the metal covering.

4.  The metal covers can be easily removed to prevent the spark voltage from shorting out.  The metal covers are a disaster in an area of any humidity.  I used a cheap rubber cap called “Sparky” in the old days and have no idea if they are still available.  Many owners cared little about the originality of the cap.

Gas tanks

The mounting for the large 6.5 gallons and the small 4.5 gallon tanks have the same rear mounting bolts.  The front bolts are different.  The small tank uses a 100 mm long bolt, and the large tank uses a 70 mm long bolt.   Both are 8 X 1.25 threads.

BMW motorcycle sidecar mounts

All of the motorcycles produced with Earles forks had sidecar mounting lugs from the factory.  In 1968 when BMW supplied motorcycles with telescopic forks, the sidecar mounts were not included.  This is for a very good reason.  Sidecars and telescopic forks don’t work well together.  In fact, they work poorly together.

I wasn’t working on them until 62 and had to learn all this from one of the most famous shops, Penton Brothers, in Ohio.  John Penton was a well known Enduro rider on the R27.  He set one cross country record from New York to L.A.  on an R69 in 1961 (I think).  They mentored me, and I learned a lot about BMW from them.


None of this matters if you want a beautiful, fun bike.  If you want a “concourse bike,” then you should find as much of the “right stuff” as possible.  I have been a BMW concourse judge at national BMW rallies, and these are all things that matter.  A 1956 or early 57 without these older “inferior” parts would be dead in the water.

In 1973 I restored a 1956 R69, and it had taken me 10 years to find most of the correct parts.  At the time, I owned the largest repair facility in the USA for BMW, and I had lots of exposure to parts.  It still wasn’t easy.  My thanks to the then-current owner, Peter Brewer, for his indulgence in allowing me to take these photos of his beautiful machine.

Updated 16 July 2022