308 carburettor rebuild - some specialities

Hello all,

noone asked but I would like to share some experiences

I have read several articles about carburettor repairs and rebuild, but just want to add some points I experienced during my carburettor rebuilt I recently finished.
I always had slightly damb carburettors and since other people have this too, I accepted it as normal. But one day it got worse and I found a fuel puddle between the heads on top of the engine.
Four rebuilt kits were waiting on my shelf since several months and so I started with the job.
After removal of the hood and airfilter housing, the first thing I performed was a rough inspection, which showed, that the source of the fuel leak was one of the lead plugs on the left forward carburettor. Many folks have slightly leaking lead plugs, but this one was REALLY leaky.
Another thing I discovered was, that on this carburettor the fuel amount injected through the acceleretor system was significantly decreased compared to the three other carbs while acting on the throttles.
Besides renewal of all gaskets included in the repair kits, these were the two main faults I had to eliminate.
First for the easiest, the decreased accelerator fuel amount. After removal of the top cover of the affected carburettor I found a faulty accelerator pump valve. This is a brass screw sitting between the accelerator pump jets. Inside this screw there’s a tiny ball which acts like a valve. The screw is plugged with a lead plug, similar to those on the carburettor housings.
After years and kms of accelerating some day the tiny ball ‚shot out‘ the lead plug. Since there’s no possibility to lose the bits completely as long as the top cover is installed; I found the tiny ball and plug lying on top of the carburettor housing.
So I had to order a new accelerator pump valve, since this part is not included in any repair kits. Nevertheless I tried to repair the faulty valve. Putting back the ball and lead plug and soldering the latter did the job and worked. See attached picture for the repaired accelerator pump valve.


Now for the other problem, the leaking lead plugs on the carburettor housings. It was not only the one mentioned above which caused the puddle. Several other plugs were also leaking, albeit not so bad, but I wanted to fix them too.
I talked with a Weber carburettor specialist over here and he gave me the following hint . With the help of a pin punch slightly bigger in diameter than the plug holes, one can restake the lead plugs, so that they are absolutely tight again. You have to center the pin punch on the plug and hammering very carefully with a small ! hammer restakes the lead plugs. I tried this and it worked; I filled one carburettor with fuel and waited till next morning. And ? No more leaking.
I have seen other methods for restaking the lead plugs, for instance with the help of a center punch. But the method with the pin punch has one advantage. You do not only press back the lead plug; you also act a little on the surrounding material, so that you can never lose a plug completely. For further explanation I have made a drawing you can see below.
I treated all leaky lead plugs with this method but didn’t touch any of the dry ones.
The result is - after now 3000 kms since this job – that all carburettors are absolutely clean and dry.

Finally I performed the synchronisation with the help of a procedure my australian friend Carl Jones – some of you may know him – developed some time ago and which is great help.

The difference concerning the repaired accelerator pump valve was siginifcantly perceptible when I drove the car for the first time after the carb rebuild. Throttle response was great and I wondered why I didn’t notice any problems regarding acceleration before.

Pictures below show the carbs back on the car, the repaired accelerator pump valve, some restaked lead plugs, and the plug restaking scheme drawing

Best Regards from Germany

Martin
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John;

I have read your posting prior to my job and thought about doing something similar, but couldn't find any appropriate stuff over here. So I followed the hints from the only remaining Weber specialist in Germany.

Best Regards

Martin