The different rear lights and rear light holders
Similar to other electric components of the BMW R12 and R17 we will show you different versions of the rear light and its holder. BMW was using supply components from Bosch during the war. These components have always been further developed in design and function as the years went on.
In 1935 Bosch was delivering the rear light model >> JN 5<< for BMW`s R 12 and other Motocycles of this period. These rear lights have been an advanced version of predecessor rear lights like the J 38, JN 3 and JN 4 which got in Germany the nickname “Zigarrenrücklicht” because of it’s elongated shape like a cigar.
One original thought was primarily to have an electric detachable hand light on the motorcycle that could be used at night. In the time of electrification Bosch combined the functions of a rear light, a hand lamp and the Illumination of the backside license plate. That was the reason this Bosch rear light product family got very successful and many different vehicles, especially motorcycles which were equipped with this.
Every rear light got a matching holder for the license plates. In case of the early BMW R12 a holder was used, that we can also find on earlier models like the R 11 Series 5 and R 4 Series 4.
In these original pictures the JN 5 is to see on its typical holder
Bosch was also modifying the rear lights for different requirements. That’s why we can find today JN 5 rear lights with little differences. Some of these rear lights where mounted on motorized bicycles, some
on heavy motorbikes like the BMW R12. Bosch gave them all Modell ID´s which are written on the lights. The most common JN 5 we can find today is the JN5 S25. But it was never mounted on the BMW R12. One main characteristic of the S25 is the small screwed pulp socket for a 3 w bulb, which was for the lighter motorcycles like the first NSU quick motorcycles.
In this picture above we see an original S25. Differences to other JN 5 versions like JN5 S6; JN5 S8; JN5 S12; JN5 S18 are the half round glass lense and the butterfly nut. On other versions, the removability as a light became unnecessary and so the JN 5 had only an octagonal nut like on the pictures below of an original JN5 S8.
Spare Parts catalogue from 1935 shows the JN 5 S6 for the first R 12.
Important information is the so called SWAN socket for a 5w bulb. Also JN5 S8, JN 5 S12 and JN5 S18 are all possible versions with this socket but have never been listed in the parts catalogue. The differences are marginally.
Also the first military delivered version of the BMW R12 in 1935 had the setup on the rear light
Remarkable is the thick cable which had + and – for acting as a torch. The most wirings of today don’t pay attention on this.
In the end of 1936 until spring of 1937 the rear light changed to the new Bosch rear light model JN7, which was so called “Eggshell” because of its shape.
Some time before the launch of the JN7, the holder of the license plate was changed, also in combination with the older JN5. As in many other examples, the transition was a floating process. The JN7 was firmly riveted on the holder which shows that the removability became obsolete.
The JN7 also appeared in different versions. Today we know the JN7 K1, that had as a main difference a more ornate screwed molded red lens, like on picture above.
The pictures below show a JN7 K2, that just had a red riveted plastic sheet.
All the rear lights, JN3 to JN7 got a matt white mineral-rich paint from the inside to reflect the light as you can see in the following pictures.
Today most of the rear lights are rare to find in original condition. Especially the JN7 was often thrown away and changed because it was made from thin sheet metal. Applicable traffic regulations cause changes. Stop-lights were additionally installed.