Late 55-mid 57 models

Early Earles fork BMW, /2 BMW motorcycle, wheels, Bosch Alamagne, sidecar mounts, Bosch U lens, accessory group, solo seat spring, tail light, coffee can, front fender, brake arm, spoke pattern, headlight ears, mounts, speedometer, headlight rim, battery

 

Earles fork BMW motorcycle models from late 1955 to mid 57

by Duane Ausherman

 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 an owners manual in 1954, so they had already been tested and approved for production.  They were specifically called constant wheel base forks for sidecar use.  They were introduced in 55 in Europe and a bit later in America.  Not all models were available with Earles forks from the start.  BMW was probably selling off old stock, before releasing the new models.

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This is a sales brochure, in English, that promotes the R25/3, R50, R69 and the 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 than 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 were 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.  In first gear the bike should only go up to a about 15 mph and then you must shift.  If you must shift out of first by about 15 mph then you have the correct sidecar gearing.  In mid 57 all twin models had the gearing marked “S” for Sport.  From the first models in 56 the sport 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 sport transmission was marked with a “S” in two places, 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 sport 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.  I forgot to take a photo of it.

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 diameter, 3.5 mm, not the later and stronger 4 mm.  The spoke called 3.5 mm actually 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.

In Europe 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.  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.  The larger battery was commonly added to these models.  Generally we didn’t change the battery holder to change the battery to the larger one.  We just bent the side 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 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 broke easily and most have been replaced with the newer wider ones.  The difference is where the ear widens out to meet the part that is bolted onto 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 chrome 14 mm.  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 brake arm that is vertical and 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 short ones were painted black and the longer ones were cad plated for delivery to the USA.  The early brake rod was also painted black.  The brake arm change was made to get more power to the brakes.

The short brake arm.

7.  The older front fender has only two mounting points, front and rear.  The later fenders have a mid point mount, 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 was 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.  BMW used more than one supplier for that light  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.

10.   Hi Duane…the shock covers are very slightly different from ’55 to about ’57 in-so-far as the top edge of the cover instead of a sharp 90 degree is rounded over.  It’s a funny thing, but I personally think that ’56 is more interesting than the R50S!  Stephen Ascherl

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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 that the “U” is.  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 manufacturers name on the top, in plain sight, “Bosch Alamagne” or something similar.

5.  The valve covers are very thick and heavy with casting “flash” lines in them, extending from the ribs straight horizontally out to the edges.  In about 61 the flash lines disappeared.  In 68 and 69 they had very light and thin covers.  From 56 to 69 they had 3 types of valve covers on the twins.  The R50S had it’s own cover, as did the R69/R69S.  The singles had two piece covers for one head.

6.  It should have the heavy horn, not the later “light weight” one.  I don’t remember the year of that change.  Can anybody help out?

7.  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.

8.  The carbs must have the 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.

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

10.  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.

11.  The early flywheels had a pressed in ball bearing for the timing marks.  Around 1959 they went to the cheaper to produce 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.  If you have proof of the beginning or ending dates, please let me know.  Photo by Thomas Browne, thanks.


The early headlight shell

The R25/3 had the horn mounted just behind and below 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.  This one is hard to photograph.

BMW motorcycle spark plug caps

1.  These are the stock cap used from the mid 50’s 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 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, back then, cared little about the originality of the cap.  Many didn’t want the large amount of brown showing and preferred the small black caps.  The cap on the /3 series closely resembles this cap with the metal removed.

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 the telescopic forks, the sidecar mounts were not included.  This is for a very good reason.  Sidecars and telescopic forks don’t work together at all well.  In fact they work poorly together.

That’s all I can think of now, I am sure I will recall more and post them.  I forgotten lots of this stuff.  I wasn’t working on them until 62 and had to learn all this from one of the most famous shops, Penton Bros.  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 a R69, in 1961 (I think).  They mentored me and I learned a lot about BMW from them.

Summary

If you want a fun beautiful bike, then none of this matters.  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 56 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 current owner, Peter Brewer, for his indulgence in allowing me to taking these photos of his beautiful machine.