700 header issue

[LipolyGone]

Anyone else having trouble with their header tank emptying
when there is still a 1/3rd of a tank of fuel in the main tank?
Both myself and a friend are having the same problem.
Martin

[HAWK 30]

Have you check your fuel (clunk) tube in the main tank, it could be sucking air (breaking up at the connection of the tank wall usually).
Or
Your fuel (clunk) tube is a bit on the stiff side.

[kamikaze]

The only way the header tank can empty is if there is an air leak in the system,probably the line to the main tank or clunk line.

When fuel is drawn from the header it creates a vacuum and this has to be filled so if there is a leak somewhere in the line it will draw in air. I would check or replace the pipework and also check that the clunk line isn't too long in case it's catching in the main tank and letting air in there. Also if you use tubing that's too stiff in the tank this can have the same effect.

[LipolyGone]

forgot to add engine is a ys st 91 and heli is 3 flights old.
I have used the fuel tube that came with the kit.
Engine also run's tank dry when header removed from system.

[xygax]

Must be an air leak in the header... you have removed it from the system and the engine dosent have problems with the main tank so the bits you have left are the header header clunk and the little bit of pipe...
Marks had a s/h rubber bung so it may be sucking a little air around it... Watch the pipe that comes out of the top corner of the tank i have seen some vary thin plastic in that area check its not got a minuite pin hole there...

Steve

[LipolyGone]

but the tank still has lots of pressure in it after 10 mins sat on the table so there cant be an air leak steve.

[snapshot]

The only time this has happened to me, has been when the main tanks clunk line has split and/or come away from the bungs nipple.

That, however, was on a 600 using an OS50 and muffler pressure.

[heliphil]

look at it this way - the header tank is collecting air from the main tank - now all you have to do is find out where its coming from.

[xygax]

Its but a dumb thaught... is the main clunk line too long and causing the clunk to get stuk in the corner during violent 3d manovers you subject the poor thing too...

Steve

[snapshot]

..and if it is only happening when there is a 1/3 of a tank left, the air leak is somewhere above that fuel level!

[SRH990]

Do you have a problem with vibration? My 700's main tank looks like the inside of a washing machine in idle-up. I'm also running a pressurised system so the engine runs consistently but because of the vibration I end up with around 1/5th of a tank of air in the header, pressure is still good at the end of the flight so it's down to vibration induced air bubbles from the main tank.

[LipolyGone]

Cant realy say as it was only first two flights with header on it before i removed it.
Is it ok to not run the header tank? Will the ys cough and stop if it gulp's a little air now and again?
Martin

[Benjy]

Yes the problem with the 700 when it first came out was that the tank was very tight inside the frames so rubbing the frames down a little seemed to take away alot of the foaming inside the tank and help with the pressurisation problem. Check to see how tight the tank is in the frames and if need be lossen it up a little and see how you get on then!

[Benjy]

BTW I have an YS SR in mine (Pumped) and touch wood not had a single problem in the 8 months of running it.

[snapshot]

Cant realy say as it was only first two flights with header on it before i removed it.
Is it ok to not run the header tank? Will the ys cough and stop if it gulp's a little air now and again?
Martin

Either use an O.S. bubbleless clunk or a fuel magnet instead.