Repairing a fuel tap of a friction roller driven mobylette Word document in Dutch

Editor Dutch version
Bob Moesker
Loggerstraat 65
1503 KB Zaandam
NEW ADDRESS k.moesker@kpnplanet.nl

Translation
H.van Kessel (2nd edition 29th 0f August 2002)
info@pantin.nl

During restoration of my Mobylette type BG 44 Fiets-O-Matic from 1962 I found a manually operated fuel tap. Not very convenient, reminding the location of the tap behind engine covers.
After a long quest I finally discovered a tap, but as Mr. Henk van Kessel already had predicted this one would show some leakage, too
As I insisted to use this original tap, I decided to try to repair that tap, though the construction does not allow that. Nevertheless I succeeded in restoring it and by way of this article I want to share it with you.
 

How to repair the tap

Step 1: filing
The aluminium casing and the copper spring holder have been attached by way of a casted flange at the casing. Exploded viewThis flange has to be removed by using a file. Stop as soon as you notice the copper lower edge of the spring holder. Remove carefully the total flange around. Remove patiently the spring holder. Now all parts are reachable.

Step 2: replacing the membrane
The dried rubber membrane should be replaced by a real membrane made of Viton or Nitril rubber. A socket for a 12 mm water pipe can be used. Of course it must be grinded and provided with a sharp cutting edge. The original membrane had a thickness of about 0.7 mm. We will replace it by a new Nitril rubber membrane with a thickness of 1 mm and a diameter of 12 mm. When you cannot find this type of material you should contact the author. The joint between the nut and casing is often dried, too. This joint should be made of 4 mm Nitril. With two hollow pipes with a diameter of 6 and 9 mm you can make this ring. Finally you can bring the thickness back to 3.5 mm with a piece of glass paper.

Step 3: checking parts and membrane
• Clean all parts and assemble them in the casing.
• Check if the free stroke of the membrane is long enough to shut off the central hole
• Push the membrane in its shut-off position with help of a adjusting tool.
• Check the position of the membrane by sucking on the little hose pillar.
• Check the angle of the sleeve of the spring holder (should be 90° compared to the hose pillar.)

Step 4: Repairing flange Repairing the lost flange with liquid metal
• Wrap some tape around the casing and rod, where no new metal will be required.
• Add the fluid metal on the casing. Avoid air bubbles.
• After the fluid metal has become very hard (see prescription of your used fluid metal) you can remove the obsolete particles with a file.

Step 5: End of assembly
• Fix the tumble plate.
• Check if the tap shows any leakage, when fixed into a petrol tank.
 
 
 
 
 
 
 

I wish you lots of success!

Bob Moesker.
 
 
 

Click on next drawing for a larger one!