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motaman38
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VBMWMO #9318
Joined: 08/31/2017
Posts: 8

I am having an ongoing issue with fuel leaking from my right-hand Bing carb.
Typically, at starting, I turn on the fuel petcock "on" , both sides, then start the
bike, and I see fuel seeping thru the braded lines (saturated), then leaking onto
the ground. (it appears that the float is not shutting off the fuel supply).

I replaced the float and pin, since this issue was occurring occasionally from last season.
The leaking issue remains.

What should I be checking here? Help!

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Motaman

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6652
Seems to me that your issue

Seems to me that your issue is that the braided fuel line has internal cracks. Over time, it does break down. Try a new run of line...I think Vech at Benchmark Works sells it...possibly Bing does. If I recall, older VW bug places sells the braided fuel line. I think you can substitute 1/4" fuel line, but you'll probably need clamps at either end since the ID of the line doesn't fit the petcock outlets.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

dardaris2725
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VBMWMO #2725
Central NY
Joined: 10/27/2006
Posts: 40
braided fuel line

I've always preferred the look of the black braided fuel line on my BMW's. However it doesn't seem to hold up with the ethanol found in most gas these days. I get about 2 seasons on a fuel line and then it starts leaking through, soaking the fabric. I've located various ethanol safe fuel lines at bike shops.

tmb3
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VBMWMO #9455
New Braunfels, TX
Joined: 05/05/2018
Posts: 1
Is your carb cap the style

Is your carb cap the style with the lever or the style where the float stem itself physically blocks the fuel line? I happen to have one of each on my bike (1958 R69), not sure if that's standard or a previous configuration problem. I solved leaks in each kind recently:

if you determine that the fuel line itself is not the cause, then double check your assembly of the float and cap. It's possible to put the lid on there without the float stem inserted into the lever or, in the other type of cap, inserted into the fuel inlet itself. You've probably checked this already, but I've screwed it up so thought I would mention it.

I found that one of my floats (right side) was compromised and full of fuel. You say you just replaced it, so that's probably not the cause. FYSA, I ordered replacements from vintagebmwparts and also ordered some modern drop-in substitutions from Bob's BMW to use in a pinch: plastic 7g floats

In my lever type cap, the shut-off pin near the hinge of the lever had created a small dimple over time in the lever itself, such that the float was having a hard time making enough force to overcome the dimple, recess the pin, and shutoff the fuel. I smoothed it out as best I could and it seems to work more consistently now.

Obviously any debris in that pin recess area can disrupt fuel shutoff even if the float, lever, and pin are otherwise working correctly.

I don't know how helpful any of this is, but I feel your pain. I'm happy to report that as of today nothing is leaking...well, fuel anyway. Smile

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Don't change, just get better. -PG

Airhead77
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Brisbane, Australia
Joined: 07/24/2013
Posts: 79
Change fule lines

If the floats were sticking you'd have fuel flowing from the overflow hole on the bottom of the bowl, not upper on the fuel line. It's the same hole fuel runs when you tickle the carbs before startup. IMO it can't be the floats. Change the fuel lines.

I had a similar issue on my 1972 R50/5 on May. The right side fuel line let petrol flow freely down. I managed to limit it by shutting down the right side petcock and got home unburned. I couldn't get a correct size braided fuel hose here in Brisbane (freaking imperial sizes everywhere) and got one from Sydney. It balooned with fuel on the first ride and leaked from every single piece of hose! Got my money back and put a simple plastic one. I'll get a period correct one when I have an order ready for Ulis.

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Current: 1972 BMW R50/5
Sold: 1960 BMW R27
Christos @ Brisbane, Australia

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