Air Bubbles in Fuel Line

[TTR_Newbie]

Just a quick question, I am finding that the fuel line between fuel tank and carb has air bubbles in it, say 1 bubble in every 1.5 inch of fuel (if that makes sense).

Should this be happening?
Is this a symptom of anything?
How can I solve it?

Any help very much appreciated.

p.s
Following up from my last post, the engine now runs when started but is a nightmare to get going, does anyone else have problems with the irvine 36.

[JaseGill]

Hi,

Could be vibrations in the frame. If there are vibrations then chances are the fuel in the tank is vibrating and frothing up.

If you cant see froth in the tank then you could have an airleak between tank and carb allowing the air in to make the bubbles.

Do you have a header tank fitted? This can solve the problem but its best to find the source first as vibration (if it is that) isnt good for the model as it is.

Hope this helps a little,

Rgds,

Jase.

[Stuart]

I'm assuming that when you fill up you fill via the header, so that you have a completely full header, that then feeds into the main tank.

Look around the seal on the header, wipe your hand under the header and see if you have any fuel on the bottom. One sure sign of a leak will be your header starting to empty before you main does.

Do you have another header you can try out.

[TTR_Newbie]

Hi all, thanks for the tips, however I see no froth in the fuel tank and don't use a header tank (should I).

Please advise.

Cheers

[Mack]

I have a Irvine 36 and have had no problem with it. If you are getting bubbles in the line it can only be sucking air in between the clunck and the carb. Check all the connections. I found a small split on one of my fuel lines once. What heli do you have?

[Raptorite]

My guess is as Mack says. Over a period of time the nitro in the fuel attacks the silicone of the clunk line inside the fuel tank, eventually it becomes very soft and splits.

In your case I bet what is happening is the clunk line has split reasonably high up on the pipe, so as the fuel level in the tank drops below the split it will then start sucking air into the carb.

The fix for this is to take the fuel tank right out of the model, take the feed nipple out that the fuel line to the carb connects to and remove what is left of the clunk out of the tank. When you replace it you will need to pay attention to two things, first the replacement pipe you use needs to be the same thin bore as the original clunk line as regular fuel pipe you would use for the normal plumbing is to think ands stiff and wont allow the necessary flexibility of movement. The second thing you need to look at carefully is making sure that the length of the replacement clunk line is identical to the original, as it needs to have the pick up so it reaches the corners of the tank when it is tilted slightly.

Normally speaking clunk lines need to be checked and / or replaced every 2 to 3 months depending on how much flying you do with the model, especially if you have a tendancy to leave a little fuel in the tank between flying sessions.

I hope this helps.

Cheers,

Pete.

[TTR_Newbie]

Many thanks all for the suggestions. Regarding the clunk and line that sound very likely as the fault as its not been replaced for say two years.

I will take it apart at the weekend for a closer look, good job you mentioned the different line (would have used thick walled).

ps

I have a Thunder Tiger raptor 30 v2.