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Home✈️Aircraft🚁HelicopterAlignT-REX 600N › Fuel draw problem
02-23-2010 01:51 AM  10 years ago
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jasonrusso

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Haverhill, Massachusetts

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Fuel draw problem
I have a 2 600Ns, both with .50 Hypers. When the tank is above the middle, I get a siphon effect into the carb. If I land and kill the engine, I have to quickly shut off the fuel feed or the engine will flood. If the tank is nearly empty, then there are no problems. Is this normal, or is there somthing not right here. I also installed header tanks (which are mounted so the feed line is below the carb nipple), and I get the same result. The header tanks were not installed for this problem, but for a couple "flame outs" with low fuel and sudden flips/rolls.
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02-23-2010 02:45 AM  10 years ago
Ladymagic

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South Korea

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I also own 2 600s with hyper 50s. That is not normal in my case. Sounds like a gravity issue though. My fuel doesn't usually flow once the engine is shut down even if it's un clipped. I use header tanks on both of mine, but I have flewn them without them with no problems. It's hard to say without actually watching what it's doing. Are the engines new? What are your needle settings? What filter are you using? Do you have a picture of your fuel setup? maybe that would help. Best bet for now is to try and lean in your needle valve a few clicks and use a fuel clip. That's assuming theres not a problem somewhere else in the fuel system. Your exhaust or exhuast pressure line could be an issue too. Check your fuel tank's exhaust nipple (on the top right side of the tank)and make sure is not blocked by excess plastic. It could be that your tank is over pressurizing and the pressure is not being relieved fast enough after shut down. Yeah, just your exuast nipple for blockage. Use a small alen key and see if you can push it through without alot of resistance. Also check your filter if it's directional and installed correctly. It's just a shot in the dark but maybe it'll help you out alittle bit.Mellisa
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02-23-2010 03:12 AM  10 years ago
jasonrusso

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Haverhill, Massachusetts

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I use the align 3 way filter, and it is installed correctly. I'll have to check the pressure nipple on the tank. I use the Align pipes. I was flying this weekend. and I was having a hard time setting the needles. It seemed really rich, and all I had done was replace a leaking head gasket. I leaned the needle in until it was about 1/2 a turn from closed. I am a little scared to go leaner than that, because I have burned a piston in the past.

Here are some pics of my setup. You can see the header tank is lower then the main tank. I had the header tank mounted higher this weekend. I thought that was the problem, but I bypasses it, and still had the same problem.

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02-23-2010 03:42 AM  10 years ago
dkshema

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Cedar Rapids, IA

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What's up with your low speed needle setting, it appears to be about as rich as you can possibly get it?

The "low" speed needle factory setting is with the slot of the cam parallel with a line going straight down the venturi. The adjustment range is only a quarter turn either way from that setting. CCW makes the idle rich, CW makes it lean. It appears that you have turned that cam as far to the left as you possibly can, making your idle extremely rich. I'm surprised your motor actually even starts, runs, idles, and transitions well to full throttle at that setting.
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Dave

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02-23-2010 03:47 AM  10 years ago
HiroboFreak

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Central Coast, NSW, Australia

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+1

Sounds like a very lean high needle (1/2 turn) to compensate for an extremely rich setting on the low valve.
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02-23-2010 03:55 AM  10 years ago
Twrecks600

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Round Rock, Texas

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Correct me if I am wrong but shouldn't the header tank fuel tube outlet be located above the carb? That is how I have mine run and I have never had an issue.
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02-23-2010 04:13 AM  10 years ago
dkshema

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Cedar Rapids, IA

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From my old planker days, the center line of the fuel tank should be on the center line of the needle valve to insure that your motor runs just as well when you're right side up as it should when you're upside down.

The header is nothing more than a wide spot in the fuel line. Where it's placed shouldn't have much of an effect on the overall fuel flow. The middle picture shows the center line of the tank just about (maybe even a hair lower) than the center line of the main needle valve.

I believe the low end is extremely rich, and the lean main needle tends to support that theory.

Set your main and low speed needles back to the factory setting. And make sure that you have the cam of the low speed needle set correctly. When properly set per the factory setting, the slot of the cam will be parallel to a line running down the center line of the venturi, and the pivot point of the cam is located between the cam body and the crankshaft. If the cam has been turned too far, you'll find that the cam's pivot point is above the cam body, closer to the inlet of the venturi, with the cam body between the pivot and the crankshaft.
-----
Dave

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02-23-2010 12:33 PM  10 years ago
jasonrusso

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Haverhill, Massachusetts

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I will set it back to factory settings and give it a go this weekend. I bought the heli used, and never gave the low needle setting a thought. It ran fine when it was warm, but doesn't now. The flooding has always been a problem.
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02-23-2010 08:29 PM  10 years ago
Jasper7

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Birmingham , UK

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Low end needle, it needs to be at 12 of just coming up to 12. In line with the egine. (Turn it 90 deg.

Don't forget to richen the Main up to abouy 1.5 to start then lean
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02-24-2010 12:30 AM  10 years ago
jasonrusso

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Haverhill, Massachusetts

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How does this look? 1 1/2 turns out on the main. I will hopefully give it a try this weekend. On my other heli, I cannot even turn the low end needle. That one runs fine, so there is no need to mess with it. It is in the factory position anyway. How does the location of the header tank look?

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02-24-2010 01:04 AM  10 years ago
Thumpernator

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Senoia, Georgia, USA

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On my other heli, I cannot even turn the low end needle
That adjustment screw is Loc-Tite'd from the factory and takes a little effort to break it loose.
Dave
I keep on thinking, but nothing's happening. Knuk, Knuk, Knuk
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