Air in my fuel lines

[Zack]

Im running clear tubing on my bike and notice that there are air bubbles in the line when the bike is running, but for the life of cant figure out where its sucking the air in from and ideas?
It is a vacuum petcock...bad diaphragm?

[t3rmin]

Are you low on fuel? Try filling up and see what happens. Are the bubbles rising up from the bottom or coming from the top?

[SqDancerLynn1]

My guess would be the fuel line is too long!

[mortation]

My guess would be the fuel line is too long!

Do you know what the recommended length for the fuel and vacuum lines is?

[bwringer]

Stop worrying about it. There's always an air bubble in there.

Or get fuel line you can't see through if it bugs you.

[Zack]

The vacuum line from the carbs to the petcock is longer then it needs to be, Its almost 10 inches, only needs to be about 6 will the extra length create the problem?

The air bubble are coming from the tank then traveling into and down the line

[Dave8338]

The vacuum line from the carbs to the petcock is longer then it needs to be, Its almost 10 inches, only needs to be about 6 will the extra length create the problem?

The air bubble are coming from the tank then traveling into and down the line

If anything, the extra length of the vacuum line will lesson the vacuum pull at the petcock, still having nothing to do with what you are seeing (bubbles) in the line. As Brian mentioned, buy some oem black lines if it will make you feel better.

[t3rmin]

If you're not leaking gas, the only way I can see you'd be able to have bubbles coming from the topside is if the fuel tube was sticking up out of the gas pool and it was burbling as it went down (ie: you're low on fuel).

[bwringer]

I still have no idea why you think this is a problem -- even with a fuel line of the proper length, there's usually going to be an air bubble trapped in there. It doesn't impede the flow of fuel in any way.

As the fuel flows, the bubble jiggles around, but, I repeat, it is not a problem -- it is simply the normal behavior of a low-pressure fluid in a tube of that shape.

In a high pressure system or a system with a pump, like plumbing, power steering, a radiator, or fuel injection, air bubbles are Bad News. In a gravity feed system like a GS, bubbles are natural, normal, expected, and not worth puzzling over. There's never need to bleed or vent the fuel system.

If you're having fuel delivery problems, you likely have an inline filter that's clogged or unable to flow enough (remove), a bad petcock (replace), dirt/rust clogging the lines or the screens over the needle seats, or a kink in the line when you lower the tank into position (shorten and/or replace).

If the bike is running fine and not leaking gas, find something else to worry about.

Of course, if we've misunderstood your problem, please give us more information.

[chef1366]

Fix it till it's broke.\\/

[KEITH KRAUSE]

Only time you'd see air is if the main petcock tower or the reserve tower was above the fuel level.

[earlfor]

Gas is a fluid and air is a fluid. The length of fuel line you use will not change the amount of fuel that flows thorough it. Neither will it change the amount of air that flows through a vacuum line.

Earl

If anything, the extra length of the vacuum line will lesson the vacuum pull at the petcock, still having nothing to do with what you are seeing (bubbles) in the line. As Brian mentioned, buy some oem black lines if it will make you feel better.

[Dave8338]

Gas is a fluid and air is a fluid. The length of fuel line you use will not change the amount of fuel that flows thorough it. Neither will it change the amount of air that flows through a vacuum line.

Earl

Mass Flow versus Volumetric FlowMass flow measures just what it says, the mass or weight of the gas flowing through the instrument. Mass flow (or weight per unit time) units are given in pounds per hour (lb/hour), kilograms per sec (kg/sec) etc. When your specifications state units of flow to be in mass units, there is no reason to reference a temperature or pressure. Mass does not change based on temperature or pressure.

However, if you need to see your results of gas flow in volumetric units, like liters per minute, cubic feet per hour, etc. you must consider the fact that volume DOES change with temperature and pressure. To do this, the density (grams/liter) of the gas must be known and density changes with temperature and pressure.

When you heat a gas, the molecules have more energy and they move around faster, so when they bounce off each other, they become more spread out, therefore the volume is different for the same number of molecules.

Go To Mass Flow Instruments

Think about this: The density of Air at 0°C is 1.29 g/liter. The density of Air at 25°C is 1.19 g/liter

The difference is 0.1 g/liter. If you are measuring flows of 100 liters per minute, and you don’t use the correct density factor then you will have an error of 10 g/minute!

Volume also changes with pressure. Think about a helium balloon with a volume of 1 liter. If you could scuba dive with this balloon and the pressure on it increases. What do you think happens to the weight of the helium? It stays the same. What would happen to the volume (1 liter)? It would shrink.



To the effect that it even matters to the petcock, NO it will make no difference. However, to be precise and accurate, the length of line (in technical measurements) will have an effect on vacuum as it pertains to volume or the lack there of. 8-[

Dave

[mortation]

Mass Flow versus Volumetric FlowMass flow measures just what it says, the mass or weight of the gas flowing through the instrument. Mass flow (or weight per unit time) units are given in pounds per hour (lb/hour), kilograms per sec (kg/sec) etc. When your specifications state units of flow to be in mass units, there is no reason to reference a temperature or pressure. Mass does not change based on temperature or pressure.

However, if you need to see your results of gas flow in volumetric units, like liters per minute, cubic feet per hour, etc. you must consider the fact that volume DOES change with temperature and pressure. To do this, the density (grams/liter) of the gas must be known and density changes with temperature and pressure.

When you heat a gas, the molecules have more energy and they move around faster, so when they bounce off each other, they become more spread out, therefore the volume is different for the same number of molecules.

Go To Mass Flow Instruments

Think about this: The density of Air at 0°C is 1.29 g/liter. The density of Air at 25°C is 1.19 g/liter

The difference is 0.1 g/liter. If you are measuring flows of 100 liters per minute, and you don’t use the correct density factor then you will have an error of 10 g/minute!

Volume also changes with pressure. Think about a helium balloon with a volume of 1 liter. If you could scuba dive with this balloon and the pressure on it increases. What do you think happens to the weight of the helium? It stays the same. What would happen to the volume (1 liter)? It would shrink.



To the effect that it even matters to the petcock, NO it will make no difference. However, to be precise and accurate, the length of line (in technical measurements) will have an effect on vacuum as it pertains to volume or the lack there of. 8-[

Dave

How many monkey fit in what barrel??????

So the short answer is yes your Vacuum and Fuel lines need to be the correct length? And the length should be?

[Dave8338]

How many monkey fit in what barrel??????

So the short answer is yes your Vacuum and Fuel lines need to be the correct length? And the length should be?

The shortest possible length ( within reason) without kinking the lines. :-D