Technical Information Pages for the Restoration of the Zündapp KS 600 and KS 750.


Editor:   ERSATZTEIL- DIENST   Hans-Peter HOMMES       D-41748   VIERSEN   Tiefenstraße 10       Tel. 02162 - 8100933

Monthly available on our website.  


Function of the fluid bearing




© 2013 h-p hommes


The function of our fluid bearing system for the Zündapp KS 750/KS 600er crankshaft.

The structure is referred to as hydrodynamic. This means that the oil pressure for the fluid bearing only builds up at the turn of the shaft in the bearing.

Explanations by the example of the vertically loaded  hydrodynamic oil radial journal bearing

for further information see Wikipedia:

Everything clear?

I just want to furnish the proof for the eternal doubters that the systems we offer for the KS 750 and KS 600 engines are not a gimmick from us but widely recognized technique.



Micro roughness on the surfaces of the shaft and the bearing shells retain the lubricant.

Tests have shown that too smooth or even polished surfaces reduce the bearing capacity and durability of the bearings.



Oil pressure and forces in a hydrodynamic radial fluid bearing

Diameter difference between bush and shaft (drawn exaggerated),
In reality only approx. 3‰



It is important in this system that there is always enough oil supplied.

This is achieved through our gear oil pumps (KS 750 order no. 1015 and KS 600 order nr.4626) ensuring a coordinated capacity for the engine.

The pressure for operation of the fluid bearing builts itself up during the rotational movement of the connecting rod on the crankshaft.


When we measure the oil pressure on the engine, then we obtain a value from 0.4 to 0.9 atm only.


And that's right!


This is normal and enough. We do not have a closed oil circuit, but an open lubrication system.

It injects the oil from the crank arms and then goes to the lubrication points - bearings and connecting rods.

The oil pump must be measured so that it transports sufficient oil in conjunction with the size of the oil channels.

An oversized oil pump virtually whisks the oil with air and the oil looses a lot of its lubricating capacity.


Anyone who has problems with the fluid bearings, has usually not worked carefully.


Especially the oil channels must be opened in order to remove the dirt there carefully.

There are only damages on the bearing shells of the connecting rods when:

- There is a lack of oil.

- The dirt reaches the bearing shells.

- Oil pumps are Improperly sized.

- Rods and pistons are incorrectly mounted.


We offer:

spare parts + accessories + repair for engine, transmission, etc. of the
Zündapp KS 750 and 600

We offer:

spare parts + accessories + repair for the

BMW R75 and Zündapp


H-P Hommes Ersatzteil-Dienst
Ersatzteile + Instandsetzungen
repairing + restoring

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