Anybody ever experience an air bubble in the gas line?

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Yellow_Cad

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With twin Amal Concentrics, I'm experiencing persistant, large air bubbles in the gas line of one carb but not the other. It is good quality, new gas line with an inline cone looking filter half way between petcock and carb. All connections on the gas line are tight. Any idea what it could be?
 
Are bubbles rising or flowing down fuel line? Interesting issue one would expect fuel leak if in tank of carb bowl or hose connections. Hi heat could boil gas but can't see that happening only on one side. A real gremlin you got that may teach the rest of us something to remember.
 
Primarily one large bubble hangs out just below the inline fuel filter on the carb side. It does it with bike stone cold.
 
I always see air in my fuel lines. I can see the level in the float bowls and when it triggers to fill, I see the fuel run. I don't think this is a issue where a fuel pump maintain pressure and a return line as with a closed fuel injected system.

I think air is evident showing atmospheric equality necessary in a normally aspirated fuel delivery system. If no air is seen I would think that there may be a venting issue.

Is the bike running poorly in this regard?
 
Primarily one large bubble hangs out just below the inline fuel filter on the carb side. It does it with bike stone cold.
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oHhh, that kind of stationary bubble. Ugh mine were due to clogged slow flowing fuel taps, so I was seeing was fuel flowing around the bubble just enough to keep it down but not enough to flush into fuel bowl. Check a rag didn't get sucked onto drains : ) I have had a big winged moth do that.
 
Is the bubble on the primary or reserve side? Does it matter if you turn them both on? You said that it happens when it's cold, does it clear after you ride for a while? I can see where a bubble might have some difficulty rising past a filter element but you'd think that if both taps are opened that it would. As mentioned, you might want to check the petcock filters, especially the one above the bubble.
 
My bubble allowed normal to high speed running fine as fuel still flowed to bowls from dual fuel line paths.
Seems I remember the petcocks seals had swollen or decayed and fitted fancy new ones that removed bubble.
I learned the hard way not to store petcocks dry but in sealed jar with gasoline to stay soaked or seals dry out wilt up and never fluff back to seal again. I have not yet learned to repair petcocks nor want to.
 
I have noticed a bubble on my reserve side often when I am tickling the carbs, opening the petcock does not seem to clear it. I have tried as hard as I can to starve the bike for fuel and it doesn't seem to matter. Of course I have never watched it while riding.

I have the fuel hoses that go directly between the Amal banjos. No "H" pattern.
Russ
 
My H hose did not remove the bubble but I think allowed full fuel flow at least below red line runs. I've tapped vigorous on the bubble to get it to creep up to petcock but tended to just move back down when tap opened. I've had this happen
in old outboards and go carts and lawn mowers too. Sometime stopped their go.
 
Yellow_Cad said:
With twin Amal Concentrics, I'm experiencing persistant, large air bubbles in the gas line of one carb but not the other. It is good quality, new gas line with an inline cone looking filter half way between petcock and carb. All connections on the gas line are tight. Any idea what it could be?
Click to expand...

You don't need an extra filter in the line as long as you have the usual filters on the tap & in the carb. banjo.
I have black fuel line so I wouldn't know about mine.
 
Open both taps and it should go away if not fit black pipe and don't worry.

Cash
 
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