Zundapp KS750, an unusual restoration project

An article from Simon Duerden about the restoration of a Zündapp motorcycle. Simon is one of the volunteers at our Wings of Liberation museum and helps to restore vehicles from WWII.

The Dutch Wings of Liberation museum lies 10 km North of Eindhoven. It is dedicated to the airborne landings in the Southern area of Operation Market Garden and also covers the invasion and occupation of the Netherlands. There are many restored Allied and German vehicles displayed, but my concern was the restoration of a Zündapp motorcycle combination.

In 1939, the company was asked to design a motorcycle combination to a military specification and submit it for evaluation. Using experience from earlier models, particularly the K800, the KS750 was produced and submitted for trials. It was a unit construction, OHV ‘boxer’ format with shaft drive, hydraulic brakes on the rear and sidecar wheels and a drive shaft to the sidecar wheel. It weighed a massive 420 kg empty with a 4 speed gearbox with both foot and hand change levers, a low ratio cross country gear and reverse. It probably needed all this as the engine produced only 26 bhp! The bike was hugely successful and approximately18,700 were made, including nearly 400 after the war. BMW produced 15,500 of the very similar R75 model, but this was inferior to the Zündapp. It was decided that production of the BMW would cease after 20,000 and effort concentrated on the Zündapp. War ceased before this happened.

Forgetting the old army expression that a volunteer is a man who did not understand the original question, I collected the beast from the museum store.

 

First, I decide to photograph everything before jumping in with the WD40, spanners, grinding wheels etc. The original idea was to restore it to a roadworthy condition, but it soon became obvious that during a previous ‘bodged’ restoration, many important parts had been lost. The plan, thus, was to do a ‘cosmetic’ restoration divided into three phases: strip, de-rust and prime and paint the bike; de-rust and prime and paint the sidecar; assemble the completed parts. All well and good, except as I started the first phase, the words ‘disaster area’ began to predominate.

These photographs show the oxidized state of the engine and gearbox, and the very corroded rear end. The brake reservoir is shown on the right, and the main drive shaft on the left of the reservoir.

 

At last, the various parts were de-rusted, the wheels grit-blasted, everything given a coat of red oxide primer and finally the top coat. The sand colour was used in both North Africa and Europe and as the Waffen SS were involved in the invasion of the Netherlands, it was decided an SS colour scheme be adopted. On a more mercenary note, we had a lot of this paint left over from the restoration of a German anti-aircraft gun!



The oxide on the aluminium parts was removed by steel wool impregnated with a special polish for classic bikes, although Brasso would probably have been as good.

The next phase, the sidecar, was by far the most difficult as the chair was 60% metal, 30% rust and 10% polyester filler from the first ‘restoration’. Replacement sidecars are available, but cost more than 1200 Euros, so a comprehensive cutting and welding exercise became necessary.



With the assistance of another ‘volunteer’, the really bad bits of metal were removed and new pieces welded in. As this was almost all double curvature, a lot of bending and cutting was necessary. This was the longest phase of the whole project and the most boring. During the restoration of the bike, I had learnt from two professional painters that a good finish depends entirely on preparation, preparation and yes, yet more preparation. Even after much rubbing down, I was unable to do achieve a pristine finish, but, I argued, this was a working war machine, not a parade bike.

It was fortunate that the museum has a BMW R75 and 70% of the parts are interchangeable with the Zündapp. I used the BMW sidecar to make templates of the seat and some other small parts.



It was necessary to buy some parts that could not be made. All spare parts are available and at a reasonable cost. The Dutch Zündapp dealer supplied a metal storage box and two original attachment clips and some other smaller items. At last, the sidecar was ready and assembly could begin.

I was now very glad that I had taken so many photos during the stripdown. The first part of phase 3 was to assemble the bike and side car attachment. The workshop at the museum is well equipped and the assembly was easy, particularly as most of the original bolts had been ground or cut off and new bolts used in the assembly. Next, on with the ‘chair’ and it was time for a photocall.





The total time was in excess of 180 hours, working virtually alone. Would I do such a restoration again? Yes, as I learnt a lot during the task, particularly about paint finish.

The bike has been placed alongside the BMW in the museum.

So if you are travelling between the channel ports and Germany, do call in.

Simon Duerden