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Old Apr 11, 2013, 09:40 PM
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United States, OR, Canby
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Going inverted might not have been the issue. I assume you gave it full throttle in the loop, if lean that could have caused it to stop by the time you got to the top. Try some full throttle passes and see if the rpm starts to sag.

One of my planes would start to sag when I went to full throttle so I gave it a little more fuel on the HSN and that fixed it. Then I let a friend fly it who is more aggressive, he had a dead stick after 10 min. tops. I flew it again without changing anything and flew 15 min. my style without a problem.
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Old Apr 12, 2013, 04:14 AM
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Germany
Joined Sep 2010
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Today I ran the plane in my workshop, which I thought might make the consequences of another dead stick less dangerous. So first I set up the carb to have a crisp response when upright. I should mention that I have my carb installed 180° rotated—diaphragm up—which gave me a better position for connecting the throttle servo.

Well, the plane was running quite well and the response was good. Holding the plane up like in hovering I could not that rpm dropped or something else occurred. But once after going back to idle reopening the throttle made the engine hesitate.

When I turned the plane to inversed position it was even worse. Being turned around at rpms above idle made no difference but transition from idle to WOT was even worse.

I am quite shure that these issues might be cured by richening up the mix but the question I still ask myself is: is this leaning out normal?

Even if the carb would pull air from the tank due to a stiff clunk or whatever it would take several seconds—so this does not seen the reason.

Stefan
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Old Apr 12, 2013, 06:52 AM
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United States, MI, Waterford Charter Township
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I'm not sure why you are hesitating to try going a little richer? I think it must be understood this type carb is a very simple one, not capable of delivering precise fuel metering like something more sophisticated might be? Close is about as good as you're going to get....

Agreed regarding the potential of a tank problem. I had a tank fall right off a 20cc gas powered profile and couldn't believe it ran for a good 30 seconds or so on the fuel contained in about 4" of gas line and the carb itself?
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Old Apr 12, 2013, 06:57 AM
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United States, NC, Faison
Joined Jan 2011
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What I ment by turned or rotated is the vent inside the tank should be pointed up to the top of the tank. Sometimes through tinkering or vibration from the plane it can rotate and cause issues in the fuel delivery system. It sounds to me like what was mentioned earlier, you may have a pressure problem in the drian hole on the pump cover. that cover can be rotated 180*. I would try that before soldering a tube to it and running back into the fuse.
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Old Apr 12, 2013, 08:36 AM
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Canada, ON, Ottawa
Joined Mar 2011
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Quote:
Originally Posted by earlwb View Post
My thoughts are that the Walbro carbs don't have a accelerator pump to provide that little extra bit of fuel to get them going when you try to punch the throttle, so there is a hesitation that occurs. But usually one could richen up the low speed just a little bit and it aleviates the condition. But it may not cure it completely though.

Another thought is the fuel regulator uses a diaphragm that is exposed to atmospheric pressure and inside the cowl of a airplane or even just being open sometimes, can be a problem due to the pressure fluctuations going on around the carb. So people started hooking up a fitting to the little breather hole and routing a tube back inside the fuselage so that the pressure stays constant. Pe Reivers on his MVVS.NL website has a article on it that goes into more detail. Anyway the pressure fluctuations can cause the regulator to make the engine slightly rich or slightly lean in different cases or worse where it goes way too lean.
I did this for the DLE 20 on my Pulse 125 - the write up (with plenty of pictures) is on my website:

DLE 20: Carburetor equalization

Quote:
Originally Posted by edwin1 View Post
My dle30 runs good for the most part. My problem is not getting a good low idle. The plane runs away from me on the ground. When I get the idle low enough to stay put, it will only idle for a minute or so then die, it also has dead stick issues when throttling back to idle from time to time. I dont have this problem on my other gassers, US41 and G-62's. But my dle30 and rcgf 20cc both have this problem. So I bought a new walbro carb for the 30 and will be trying it out this weekend.
Edwin
Poor idle could be the result of the reeds not seating properly, which can be fixed by lapping the gasket and reed surfaces. Also done to my DLE 20, along with another write-up:

DLE 20: Gasket and reed surface lapping
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Old Apr 12, 2013, 11:18 AM
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Germany
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@grosbeak:

When this morning I dismantled my carburetor I also thought about that lapping thing when I saw the reed block—the aluminum could be in a better shape there..

This air equalization might be another thing the overall performance might benefit from. But in my workshop I held the plane in my hand when flipping it over and in this situation the airflow around that hole should be the same in either position.

@ahicks:

I tried to richen the mix but it does not seem to keep the engine from cutting out, just makes the upright mix really bad. Fortunately my airplane design was my first one with double elevator servo. When picking up speed from the dead stick in vertical position I noticed quite a weak elevator response. Another Hitec had died on me. :-)
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Old Apr 12, 2013, 12:20 PM
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United States, MI, Waterford Charter Township
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I'm about out of ideas, but just a thought. Is there any chance the battery voltage to the ign. module could be dropping out on you? Low or too small a battery, loose connection, something along those lines?
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Old Apr 28, 2013, 01:48 PM
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Tucson
Joined Nov 2009
980 Posts
My DLE 20cc really changed idling characteristics, as I ran it more. I had to set the idle adjustment many times, to get it to slow down after running it fast. I think that it is natural for these engines to not slow down to idle immediately, from high speed. But that does make it more difficult to set the idle speed so that the plane will stop on the runway.
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Old Apr 28, 2013, 01:52 PM
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Tucson
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My DLE idle speed goes way up when the engine sucks air (then dies). Make sure that you aren't sucking air in vertical flight. (This is a long shot possibility, and can easily be eliminated.)
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