Technical Information Pages for the Restoration of the BMW R75 and Zündapp KS 750.

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

Monthly available on our website.            www.wehrmachtsgespann.de
 

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An often asked question is:

The bike runs very well, but after a short rive in fourth gear, I cannot drive faster than 60 km / h, and the engine stops after some stuttering.

What can it be?

When I wait a bit, the engine starts again and runs normally.

Is the magneto defect?

I already changed the magneto!

But the fault is still there.
 

Is petrol lacking?
When I pull the hose off petrol flows out.
So it should not be a fuel problem.
 

However, this could be a mistake.

We could even ask the question:
How much petrol flows out per hour?

There are replicas of the fuel taps that do not deliver enough petrol per hour because their flow rate is calculated incorrectly.
But also good-looking original parts can suffer from “constipation”.
The original drawing of the fuel tap indicates 22 liters per hour.
According to my experience approx. 14 liters are already sufficient.
The problem of faulty fuel taps is often not recognized.
 

How do I measure the flow?
It's simple.

Take a beer glass with 0.2 liters, look at your watch and determine how long it takes to fill the glass. It should not be more than 50 seconds. Anything that needs more time could lead to an insufficient supply of fuel at full throttle. When you stop your bike at too little flow, the fuel is slowly dieseling and the engine works again for a while until it is missing petrol again.
A brass sieve filters the dirt parts out of the petrol so that they cannot get into the carburetor.
Dirt and water collect in the removable filter housing.
Therefore the filter housing of the fuel tap should be cleaned regularly.
 

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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