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Discussion Starter #1 (Edited)
Very strange story!
My float valves do not close well. The carburetors overflow when the engine is running idle, because the consumption is less then the leaking quantity. My first thought was, the needles need to be replaced. Their rubber tips were not in perfect shape. I purchased a repair kit, replaced the bowl gaskets and the float needles. The new needles are the same size as the old ones.

The overflow did not disappear. After a lot of scratching my head, I realised, the needles cannot slide deep enough into the valve body. That thin wire clip on them touches the outer end of the bronze valve body. If I remove that thin wire clip, the needle goes 1/2 mm deeper into the hole, without any force. It seems to me, the needles are short. Unbelieveable, isn't it?

What the heck is happening here? I am about grinding 1 mm from the brass valve body...
 

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Discussion Starter #4
Guys,
the same needle was fine in the right side carburetor and short in the left. I could not believe my eyes. At last, l grabbed a - how to say in english? - tiny, flat file, and filed down the face of the left side bronze valve body. Filed off cca 0.5mm.
Now the valve opens, closes perfectly. I tested it: Turn the carburetor upside down, the floats will shut off the valves with their weight, blow into the fuel hose! Lift the left float, the left valve opens. Lift the right float, the right valve opens.
Now the carburetors are working, the bike runs well, no carburetor overflow.
 

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Guys,
the same needle was fine in the right side carburetor and short in the left. I could not believe my eyes. At last, l grabbed a - how to say in english? - tiny, flat file, and filed down the face of the left side bronze valve body. Filed off cca 0.5mm.
Now the valve opens, closes perfectly. I tested it: Turn the carburetor upside down, the floats will shut off the valves with their weight, blow into the fuel hose! Lift the left float, the left valve opens. Lift the right float, the right valve opens.
Now the carburetors are working, the bike runs well, no carburetor overflow.
The new needles are the same size as the originals and one worked in the right side carb and the other won't go down properly in the left? Sounds to me like you have the correct needles, but there may be some debris in the left valve that is preventing the needle from going in like it should. Grinding down the needle may seem to be working, but it may be masking the real issue that may come back to bite you later.
 

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Discussion Starter #6
The new needles are the same size as the originals and one worked in the right side carb and the other won't go down properly in the left? Sounds to me like you have the correct needles, but there may be some debris in the left valve that is preventing the needle from going in like it should. Grinding down the needle may seem to be working, but it may be masking the real issue that may come back to bite you later.
I measured the depths of the valve bodies. The left side valve was deeper 0.5mm. I think, the previous owner machined it down a little. Maybe he cleaned the bottom with a fraser? I do not know. But now the bike runs nice, problem solved.
 

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Discussion Starter #7
One more comment: From a carburetor owerflow, fuel flows into the cylinders, and from there, into the oil. An oil change required.
 
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