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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Header Tank Headache
09-21-2009 04:47 AM  11 years ago
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mferraz

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Houston, TX

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Header Tank Headache
I hope this is the right pleace to post this, but it's really not specific to any one heli, but more about fuel systems in general. Ok, here goes...

So, I have a 700N, with a YS91sr. I've been in fuel system hell for almost 3 weeks now. I have changed the main tank, added a header tank, changed all the fuel lines, the check valve, and the T-Filter. I can leak test with a full fill up, even cap off my preassure release towards the end of the fill, and no leaks. Ok, so get this...

When I'm in flight, and ONLY when in flight, my header tank slowly starts to empty. Not as fast as if it were doing so at the end of the flight, and before the main tank is anywhere close to empty. Within the first few minutes of flight. Main tank fine/full, header tank half empty.

Gets even weirder. The header tank stays half full and doesn't empty. Now the engine starts running super lean under throttle. I sit her down, and notice a few bubbles in the short fuel line that goes from the fuel regulator to the carb on the engine. I've heard these bubbles are nothing to worry about, but there seems to be lots of differeing opinions on ths, so I'm not really sure what to think.

The most difficult probelm about all this is, I can't reproduce it on the bench, only in flight. And a 700N isn't really something you can just fly anywhere, so I have to try something, take it to the field, test it, take it home. Everytime I do something more I and leak test, I feel like it should be good on the next flight, but do dice. That header tank keeps on starting to empty early in the flight.

So, I'm thinking maybe it's an engine issue, or something else I'm not thinking of. Before I added a header tank, I was using a fuel magnet, but it started to go bad and jack with my tuning, so I decided to try the header tank, since I have them on all my birds and am used to flying with them.

I'm not sure if I was having this problem with the fuel magnet or not, but if I was it was pretty covered up I guess. If I run direct from the main tank, it starts to lean as well.

I'm really at my wits end here, and love my YS, but this is really driving me crazy.

If anyone has had this problem, or might have any ideas about what could be causing it, or how to fix it, I would really be most appriciative. Thanks for your time...
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09-21-2009 05:03 AM  11 years ago
GimbalFan (RIP)

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Big Coppitt Key, FL

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Are you certain your clunk lines aren't so long the clunks are against the rear of the tanks, causing intermittent blockage of their intakes?op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t
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09-21-2009 05:08 AM  11 years ago
mferraz

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Houston, TX

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Yup
I have checked the clunk lengths everywhere, and change both clunks multiple times. I even tried a few K&S header tanks, which much have been from a bad lot or something, becuase they both leaked. I'm on my second thunder tiger tank at the moment...
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09-21-2009 05:17 AM  11 years ago
jesus1895

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Tucson AZ

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remove just the header tank And the magnet........
and try that.its easy and quick.....can be done at the field,See if that helps.
AMA #224344
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09-21-2009 05:18 AM  11 years ago
GimbalFan (RIP)

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Big Coppitt Key, FL

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Interesting puzzle. Welcome to The Jungle. op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t
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09-21-2009 06:50 AM  11 years ago
jbiter

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Sebring, FL

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When you fly, does the fuel foam at all from vibration?
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09-21-2009 07:12 AM  11 years ago
mferraz

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Houston, TX

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Vibration Question
Yes, but only in the main tank. The crankcase pressure coming off the backplate of the engine really seems to stir up the main tank fuel. I can't remember for sure if that has always happened, or not. I've been dealing with this issue for a while now and it's hard to remember for sure when I changed what or if it did something at a specific point, but I'm trying my best. I don't specifically remember the fuel being that stirred up in the main tank before, but I really doubt I was paying that much attention to it, really. Alomst like there is a white blur in the main tank during flight, especially while under power (climbing out, etc.)
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09-21-2009 08:17 AM  11 years ago
Hamo

rrVeteran

Ireland

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I suggest you check and double check that you have the header tank piped up correctly. In / out etc and the clunk in the header is on the right port.
Hamo
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09-21-2009 09:41 AM  11 years ago
Jeff polisena

rrElite Veteran

westpalmbeachflorida usa

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Use a bigger inside diameter line in tank motor might be starving and pulling fuel out of header tankI stole it ,flew it and gave it back ;)
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09-21-2009 09:51 AM  11 years ago
The Old Guy

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UK Surrey

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Definatly fuel foaming,
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09-21-2009 10:19 AM  11 years ago
jbiter

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Sebring, FL

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Fuel foaming will cause what you are describing. The cause of the fuel foaming is not the crankcase pressure. It is caused by vibration which needs to be remedied.

Jeff
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09-21-2009 12:57 PM  11 years ago
Jerry K

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Houston Area

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Check your rear motor bearing it may be rough enough to cause vibration which in turn is causing your fuel foaming. The YS 90ST has been reported to be a rough motor when everything is right. The motor needs to be disassembled to check the bearing so you might as well change it when you go that far. I have that bearing in stock if you want to borrow one or do it over here. I also have a bad one for comparson. You have enough time on it that may be it.

You said your fuel magnet was causing you problems at first, so you changed it. You did not state if you stayed with it, or have a regular clunk with your header tank now. Foaming in the main tank may be bad enough to pass through a magnet also let alone a standard clunk.

One thing about motor bearing vibration problems is that they crepe up on you slowly until they manifest themselves like this, in another area like a lean running motor!

http://www.rc-bearings.com/catalog/...c0ea848650ae99d
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09-21-2009 01:12 PM  11 years ago
MessyDan

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Johannesburg, South Africa

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On the 700s main tank I have noticed that the pressure fitting at the top is often blocked by plastic - and required drilling out... also have you checked that the exhaust is tight? and the pressure nipple is in good condition, tight?
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09-21-2009 05:06 PM  11 years ago
mferraz

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Houston, TX

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Magnet and Muffler Q's
When my fuel magnet went bad, I decided to forgo it in lou of a tradition clunk and header tank system. That's why I'm not sure if I had the problem before, but I'm pretty sure I am seeing more foaming now than I have before. At least, I think so.

The muffler is on tight, and it have an O-ring fitting. It's an Hatori SB, and the engine is an YS91SR. The tank pressure comes from the engine backplate on the YS, unlike the OS where it is exhaust pressure.

I hadn't thought of the engine bearing idea. If it was a vobration thing that could make sense.

I might take you up on your offer Jerry, if you have the bearing and are willing to let me camp out for a bit while I take it down.
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09-21-2009 05:13 PM  11 years ago
mferraz

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Houston, TX

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Jerry
Is the bearing you have for the SR or the ST. Are they the same bearing?
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09-21-2009 05:31 PM  11 years ago
imnxtc

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BC.Canada

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Fuel foaming will cause what you are describing. The cause of the fuel foaming is not the crankcase pressure. It is caused by vibration which needs to be remedied.
Yep - bet that is it. And it is usually a high frequency vibe, from misalignment of clutch to clutch bell or some shaft needing dial indicating to below 2/1000.
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09-21-2009 06:50 PM  11 years ago
junkpilot

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Alamogordo N.M.

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Header tank
In your original post you stated you were running a YS 91. That engine uses crankcase pressure to push fuel to the engine. You don't need a header tank! Unless you just like the look.
The tank is going down because small amounts of air are entering the tank.
Junkpilot
When you fly JUNK it's hard to tell when you've crashed!
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09-21-2009 09:17 PM  11 years ago
Furious Predator

rrProfessor

Kitchener, Ontario, Canada

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In your original post you stated you were running a YS 91. That engine uses crankcase pressure to push fuel to the engine. You don't need a header tank! Unless you just like the look.
the header tank has nothing to do with pressure, its to catch bubbles. i run headers on all my YS engines just for that purpose, which it works well at. i dont run a fuel magnet though, i find no need for one with a header. I just use the heaviest clunk i can get my hands on, lol.
uel foaming will cause what you are describing. The cause of the fuel foaming is not the crankcase pressure. It is caused by vibration which needs to be remedied
i second that.

also check that your clunk line moves free and cannot get stuck in the corner of the tank somewhere, but sits roughly in the middle.
Shawn
Team Leisure-Tech
Team HelixRC
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09-21-2009 09:26 PM  11 years ago
mferraz

rrNovice

Houston, TX

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Bad Vibrations
Alright, so it seems that the vibration could be a likely cause. Come to think of it, I changed my clutch our right before this started happening. I took the engine out earlier this week, when I changed the main tank, but didn't mess with the clutch.

What all should I be looking for in so far as the clutch, housing, and bell go. How would I look for the source of the vibration, and possibly narrow it down. Seems like it could be related to that clutch change out. I'm just not sure where I need to be looking for tolorances of 2/1000 or how.

Thanks again for everyones help and advice!
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09-21-2009 09:31 PM  11 years ago
Furious Predator

rrProfessor

Kitchener, Ontario, Canada

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do you have a high point balancer and a dial indicator?

you also need to make sure that your clutch bell is lined up as best as possible with the shoes/engine.
Shawn
Team Leisure-Tech
Team HelixRC
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