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If you have the correct size hose and have the hoses well seated on the respective tubes and nozzles, there should be no dripping at all. So, not a common problem.
Other possibilities; The nozzle on the fuel petcock (assuming the straight thru version) might have a crack at the base of it where it threads on to the housing. The horizontal outlet version is formed in the body of the petcock, so this may not be relevant if you have those type petcocks. Fiddling with the hoses could open up a crack in that part, it is made of some kind of fuel resistant plastic. Petcocks, in general, can weep fuel, especially the "Everbest" taps fitted on some 70's bikes.
Similarly, the inlet nozzle on the carburetor body can be a source of leakage, usually from failure to fully engage the hose on to the brass nozzle. My take on reading your post is that the fuel seepage starts at the top near the shut-offs. You might try opening one side, then the other to see if the problem is side-specific. Each side of the fuel line plumbing has 5 fitments where fuel can escape. 1 the fuel tap, 2,3,4, the "T" where the the crossover line runs thru the airbox and 5 the carburetor inlet. It's a pretty simple system. Careful examination of the 5 points should reveal the trouble. If you have the straight thru petcocks, I'm going to wager there is a small break in the plastic outlet nozzle.

Despite the good advice regarding a possible faulty petcock, that does not seem to be the problem.
Earlier today I ran the carbs dry with both petcocks off. Then I opened the on on the right after a few second raw gasoline seemed to be migrating up from the carburetor on the left side and most of the lower braided fuel lines were soaked. Fule started dripping. Meanwhile the area of the fuel lines at the petcocks was dry.
So its not the petcocks.
Another idea? Suggestion.

What size fuel line are you using? If it's not the correct size, you'll have this problem.

Reply to 14652:

When your reply came up in my email it was more extensive than what I am seeing on the forum. In fact the additional information is critical. It said, if I'm not using 6 mm that could be the problem. If I had just gone to the forum I would miss that and I wonder why it doesn't show up here? Any ideas.

Anyway, back to the problem.

Last week, thinking that the fuel line was leaking, I went on line and found KLASSIC CYCEL STUFF run by someone named Michael Benoit, "Specializing in Quality Parts for your vintage BMW Motorcyles". Almost immediately on the site the braided fuel line came up looking exactly line what I had on my motorcycle, along with the recommendation that 3 feet was the length needed and the specification was 7mm. How could I go wrong with a company that "specialized".

I purchased it and it arrived the next day. When I installed it I felt it was not as tight as I might have expected it should be, but it fit snugly. It was after that the leak increased to a somewhat steady stream.

You seem to be suggesting with some authority that I have the wrong fuel line installed.

I would love to hear a little more ...

I'm back again (15371).

I want to consider the carburetor before I focus again on new fuel lines, although if my lines are too big, leaking fuel would be a logical result.

Carburetor? If the float is saturated in some way, or perforated or whatever it takes to be non functioning so the needle is not lifting into the supply port then the carb would fill with fuel and the fuel would eventually fill the fuel lines all the way up to the tank. My understanding, however, as to how the system works is that even if that happened you would not have a fuel leak because everything is sealed off. Maybe I am wrong about that? Can someone answer that question?

I have never removed the carbs on my R75/7 and I am pretty comfortable with carburetor disassembly. The thing that makes me anxious is whether I can remove the Carbs and retain the accelerator and choke setting without disturbing the position of the wires as they are now set by the lock screws.

How do I navigate to the area of the web site to do some reading on the subject?

Sorry, I tried to edit but something went wrong. Correct size fuel line is indeed 7mm. No hose clamps required/recommended.

For the carbs, go to Youtube, here is one instructional video: https://www.youtube.com/watch?v=F4_C5B-SjFo

Hope this helps.

I've been using 7mm fuel line forever. No clamps, leaks....yet. But the day is still young. 😛

► If your fuel lines exit the petcock straight down rather than to the side, then you may have broken the gray plastic nipple under the 17mm nut on the bottom of the petcock. In the 6 months I've had my bike I've gone through 3 of these. Of course the tank has been on and off several times due to brake issues, but they are delicate pieces. They can fail to seal to the bottom of the petcock OR they can develop hairline cracks. Your issue sounds like the latter. Order a spare for the tool kit.

► I went to the hardware store and bough 10 of these small fuel line spring clamps. I like these better than the common screw clamp. These apply a constant tension to the hose and are usually black in color so they are invisible on the hose. I paid about 25 cents each at the local ACE hardware store.

Fuel leak solved.
With both petcocks off, I ran the carb dry (again). Then observing very carefully, I opened the right side petcock and very quickly saw fuel soaking the braided covering where the cross over fuel line connected to the t connector. Both sides.
I placed fuel line clamps on both sides. Leak stopped. I left the petcock open for several hours. Not a drop.
Here is my general conclusion. 7mm lines are adequate. They could be tighter, but 6 mm might be too tight to get on. I don't know, cause I've never tried 6. I purchased the 7mm braided line and replaced all except for the cross over, which I anticipated to be anywhere from a minor to a major challenge. With the old rubber of the cross over fuel line (it could be 39 years old) moving it off the t, which is did to more easily install the other new lines, disturbed what little tightness remained and when I reassembled the old cross over line, it just leaked more that before.

Now the question is whether to be pro-active and replace the cross over line, or just leave well enough alone since the clamps seem to have solved the problem completely.

If I were to replace the old line, my plan was to get a connector attach the new line to the old, tape the frayed braid tightly and push the new line through while gently tugging on the old - not so hard to pull it off the connector, because remember, its not a tight fit any more. So it has to be a lot more pushing than pulling.

Comments?

Thank you so much.
So what I am hearing is 6mm braided fuel line is available from the Beemer Shop. The slightly small size will make installation a challenge, but it will solve the leak and clamps problem. I assume the 1/4 inch you are referring to is better than the 7mm for reducing/eliminating fuel line leakage, but not likely to be available from the FLAPS. (? Local Auto Parts Store - What does the "F" stand for?)
The Long Phillips Head screw driver is a great idea.
With the 6mm it should thread through easily.
Whether 7 or 6 you did not mention taping the braid down tightly to avoid catching as the line is passed through.

Funny, When I think about all the accolades heaped upon the engineering and design of the BMW airheads, including my own, it takes a bit of pause and reflection to wonder who was the moron that came up with the idea and design of having to replace a fuel line that by threading it through a difficult hidden from view passageway from one side of the air box to the other. How about a tube that provides an easy threading route? How about anything but what it is.

Someone suggested it was not too difficult to remove the box to gain access and then, with the best of intentions described what would probably take at least an hour each directions for someone who was being careful and had not done it before (that's me!).

Here is a tip. When I was a first time Airhead owner, I was confounded by the way the bikes' systems were put together. After a few attempts at any thing that seems daunting, the task becomes familiar and then quick and easy. The airbox, for example, can be opened up and re-assembled in about 15 minutes after you learn, or are shown all the less than obvious tricks. If I were standing next to you, I could demonstrate the proceedure in about the same amount of time it would take to type it out. Find a tech day near you and go to ask questions.

I am not sure who or why my comment was taken as an insult.

I am new to air heads, but thought a forum, generally, was a place you could express yourself freely - although politely - without fear of someone taking offense. No offense was intended. My comment about a design flaw was the point, not someone's deficiency in proposing a disassembly I might find challenging, that would be easy for someone with more experience.

Got it. Just don't be angry with me. These days I am a little fragile because of personal stuff, not mechanical.