r90/6 fuel line question

Found the left side fuel line leaking after flipping on petcock earlier today. Couldn't tell from where exactly because a substantial portion of the line appeared saturated by the time I noticed.
Switched the fuel back off and left the bike for several hours.
Switched the fuel back on, sat down beside the bike and watched carefully with my fingers lightly on the lines to detect leakage as quickly as possible.
Nothing leaks.....hmmm? Don't know why.
Being a complete novice, I was wondering what the fuel line does that intersects the line going to the carb perpendicularly does?
Thanks

157149 said:

Found the left side fuel line leaking after flipping on petcock earlier today. Couldn't tell from where exactly because a substantial portion of the line appeared saturated by the time I noticed.
Switched the fuel back off and left the bike for several hours.
Switched the fuel back on, sat down beside the bike and watched carefully with my fingers lightly on the lines to detect leakage as quickly as possible.
Nothing leaks.....hmmm? Don't know why.
Being a complete novice, I was wondering what the fuel line does that intersects the line going to the carb perpendicularly does?
Thanks

Click to expand...

It connects the two fuel lines on each side of the engine together. I just replaced all my fuel lines due to fuel dribbling and some really slow leaking. The "proper" fuel line really does work better than the bulk stuff from Napa. You'll need about 3 ft.

Some questions:
1. Do you have the straight up and down petcock on the left side (as opposed to the 90 degree elbow)? If yes:
2. Does the metal-jacketed enrichener (choke) cable pass behind the petcock pot metal/aluminum body? If yes:
3. Have you turned on the fuel and felt for a worn ridge on the back side of the petcock where the STEEL-JACKETED cable rubs on the SOFT METAL petcock? If yes:
4. Did you just find the source of your leak on the left side?

If yes, come back here for further information.

Just checked again

Petcock looks straight up and down to me
Checked behind petcock-cable is worn to metal, petcock is not worn thru
Sat and watched the line again with left petcock on for about 6 minutes-nothing
Then turned on right petcock and watched again-still nothing

Good job. Assuming that there is no ridge worn into the back of the left petcock (if there IS a ridge, but no apparent leak, report that here) then:

Do you have the braided fuel line? If yes;
Was the braid immediately below the petcock saturated?

If yes, using a flashlight, examine underneath the tank where the threaded petcock fitting exits the tank. Any sign of dampness?

With both petcocks turned on, feel around the threaded sections of the petcock itself...any dampness?

update

The line immediately below the petcock did not appear saturated.
I'm going to clean everything up with some paper towling in the morning and examine again.
Thanks for suggestions!

ps

The line is braided-does that mean it's original?

Yes;

Braided is the original type line alright, not necessarally the original line and certainly not required. Fuel lines are available nearly everywhere theres a auto parts store. Your internal valve parts can fail too over time. Two things can be done; Buy new petcocks @ 40$ each or try to tighten the very thinly threaded petcock face that holds the internals in place. Its the knurled part under the plastic labeled on/off/res cap around the on/off lever. The plastic pops off right over the lever. If you try this, tread very light, as the threads are not much there and can be ripped too easy. It can be done however and stop many leaks....The internal rubbers can be eaten away with time and leak. Just an idea I know too well. 40+ years Airhead ownership go'in on in my garage. Randy

I'm not sure of the size difference, but I tried fuel line from my local Napa and it was kind of loose on the "T". It fit fine on the carb and the petcock. I ordered some of the braided stuff and it's a nice snug fit. Plus, I think I like the look of the braided line.

Good luck with your project.

Both Randy and Richard are correct above. The original design fuel line was the German-made 7mm inside diameter braided line. That's still available from larger parts outlets like Bob's BMW and some smaller places like Hucky's and from places that sell parts for old VW's (although I had a bad experience with some braided line I bought once from a VW car dealer...it was braided but stamped "made in Brazil" and it leaked immediately from poor fit). Meanwhile, some people go to NAPA and buy their non-braided fuel line...which is quarter inch. I tend to come up with excuses to want to remove my tank so I favor the braided for the looks and better fit. Richard is correct that 3 feet of new line will get you enough to comfortably replace everything.

If you've confirmed that the source of the leak is not a pinhole leak in the tank, not leaking past the old fiber washer in the petcock and not from a hole worn in the petcock by the choke cable armor, then you're headed toward the line replacement. This is part of ordinary airhead maintenance and needs to be done every few years. Let us know what you find.

I have had very good luck with the fuel line sold by the Bing Agency. I replace it every 4-5 years along with the plastic in-line filters (also from Bing).

http://www.bingcarburetor.com/bmw/cvaccessories.html

It doesn't have the cloth braiding on the outside, but is black and looks pretty good.

If mine were leaking as you described (and I was sure it wasn't coming from a hole in the bottom of the tank), I would start with the fuel lines.

But, when I have the lines off, I would also carefully examine the plastic pieces at the top of the lines (with the nut that attaches the lines to the petcocks) to make sure there are no cracks. I might replace them and/or the washer inside if condition looks marginal.

Not too expensive and a good routine maintenance item.

If it still leaks after replacing the lines, there is a petcock rebuild kit with the three or four rubber/cork items inside the petcocks. Not too complicated of a job and not too expensive. Again, another routine maintenance item that probably needs done every 10-15 years (yours might be due).

Finally, as mentioned above, the metal choke cable rubs (saws?) into the left petcock with the vibration. Put a two inch piece of fuel line around the choke cable to isolate it from the petcock and you will be good to go.

Here is what mine looks like, as described above.

Regards,

Barron

I had a persistent petcock leak on one side. Turns out the problem was that the tank stub outlet was not square and had some metal flash that prevented the cambric washer from sealing. I few minutes work with a flat file, and the petcock was dry once again.

More often than not, I find that my leakage and fuel line saturation is that one of the connections has become a bit cocked or twisted, not allowing a good tight seal on the fitting itself. If you found a line saturated and then came back later and it stayed dry, it would seem this is the culprit. Easy enough to just make sure the fuel line, the braided stuff, is on the fitting nice and straight with no crimping or binding.......Good luck.....Dennis

I bought a meter of the BMW braided fuel line from my dealer during my rebuild. It went on the various barbs quite snugly, and I did not feel I needed to use clamps. Two weeks later, the fuel line had swelled enough that the tubing was no longer tight on the barbs and gas was leaking past enough to cause a constant drip when the petcocks were open. It took me a while to track it down to that source, since the gas was dripping from the bottom of the float bowls.

I put worm gear clamps on all the fittings, and no more leakage.

As a side note, I was not able to get the braided fuel line to fit through the airbox hole for the crossover. It was way too large. I had to re-use the PO's clear polyurethane line there. Shouldn't the OEM fuel line fit through those holes?

geisterfahrer said:

As a side note, I was not able to get the braided fuel line to fit through the airbox hole for the crossover. It was way to large. I had to re-use the PO's clear polyurethane line there. Shouldn't the OEM fuel line fit through those holes?

Click to expand...

It does but it takes the patience of Job. Easier and quicker to remove the airbox covers when replacing that section of line. An available compromise is to use a non-braided urethane line from a hydraulics shop for the crossover line (because without the braid it'll feed through the holes easier) and braided for the more visible exterior lines.

http://www.aircraftspruce.com/menus/ap/hose_fuel.html

Bill Burke said:

It does but it takes the patience of Job. Easier and quicker to remove the airbox covers when replacing that section of line.

Click to expand...

Agreed. Since it hardly ever needs doing, just 'install' it there. Since I'm using SAE 'fuel injection' hose, it's thicker. There is no way it will even slide in the holes under the airbox. The upside is, it also doesn't noticeably loosen on the fittings because of the extra thickness and it doesn't need clamps to stay tight.

I'm guessing

Dennis may have it right based on all available evidence. Perhaps I banged it with my size 13's-i did notice it was more twisted than the right side.
No leakage today.

geisterfahrer said:

As a side note, I was not able to get the braided fuel line to fit through the airbox hole for the crossover. It was way too large. I had to re-use the PO's clear polyurethane line there. Shouldn't the OEM fuel line fit through those holes?

Click to expand...

The braided line I ordered from the Beemerworks not only fit easily through the hole under the airbox but I can slide it back and forth. No leakage from any of the joints.

After the PO's polyurethane tube decided to split yesterday I decided it was time to put the braided hose in. I had to remove the left half of the airbox and the filter, and loosen the right side to get it in. Once in place, though, everything fit back with no problems.

It's nice having the Odyssey battery -- it sure gives you a lot more room to play around with the airbox