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DLE 20cc trouble

Old 12-02-2018, 08:02 PM
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jimmy7432
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Default DLE 20cc trouble

I have a DLE 20cc engine in a Citabria Pro Balsa USA plane. I am having trouble with the engine stalling at high RPM. It runs great for about 5 minutes and then just cuts out. I have tried adjusting the high end needle valve both ways rich and lean and have the same problem. When I run the engine at high RPM and after a few minutes it starts to sputter I quickly I slow the engine down. If I time it right the engine continues to run at low RPM and then when I bring it back up to high RPM it sputters and eventually stalls. I though it was over heating at first but when I run it with the cowl off it does the same thing. I checked the clunk and that is fine. I bought a new fuel tank and tubes and reinstalled the fuel system to be sure I did not make a mistake the first time and same thing. I changed the gas to have fresh gas a few times and same thing. I have seen posts about these engines good and bad. I don't want to here DLE engines are junk because I already bought the engine so that won't help.(But I am beginning to think the engine is junk) Any help would be appreciated.
Old 12-02-2018, 08:18 PM
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Truckracer
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How old is this engine? This would help to get to the problem. Side or rear exhaust version?

The 20 is one of my favorite engines and I just ordered another one on a Black Friday sale. Its no different than any other gasser as when problems develop, they all tend to be the same regardless of brand.
Old 12-02-2018, 08:31 PM
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speedracerntrixie
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If it has run well in the past and this is a new problem, my first guess with the limited information provided is debris in the carb. Filtering fuel on a gasser is very important. Othe options would be a bad ignition battery, ignition timing being off, both advanced and retarded will cause the engine to overheat. No mention on fuel/oil mix but this engine requires 30:1 air cooled 2 stroke oil. Bottom line is that you really need to be specific to get accurate advise.
Old 12-03-2018, 06:00 AM
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ahicks
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One sure fire thing to make an engine quit is a lean condition. Figuring out why it's lean can be pretty tricky some times, as the problem can be anywhere from the fuel tank clunk to the tiny filter within the carb.

If you are getting air bubbles in the line leading to the carb, you'll need to eliminate them. The 2 common ways, are to make sure your fuel system isn't sucking air at any of the joints, and installing a felt clunk in your fuel tank. It's common for a fuel tank ti foam up at high vibration levels (like high rpm generates), and the easiest cure to eliminate any possibility of the engine sucking up that foam is a felt clunk. Most lawn equipment and chain saws run them, so they're easy to find. Here's one at Home Depot that I've used: https://www.homedepot.com/p/Maxpower...3155/301974262

If you're absolutely sure you are not sucking air bubbles, the issue is likely the internal fuel filter. It's inside the carb, on the side that one screw holds in place. It's about as big around as a pencil erasure. I usually lift one side (carefully) with the pointed end of a #11 xacto blade. There's nothing holding it in place. If you don't see any debris there, pull and clean it anyway as they have this nasty habit of accumulating some type of gel that's totally transparent.

I suppose it's also possible to put too small a prop on this engine, causing it to turn WAY to many rpms. Most people run the on 16x8 and 17x6 props.

Last, most that have one of these DLE 20's and have gotten to know them, LOVE them. Well known for being reliable, easy to handle, they make a ton of power for their size, and they are the lightest engine in this class.

I'm discounting the potential for a low battery as they go into limp mode when that happens - without quitting. -Al
Old 12-04-2018, 11:04 AM
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jimmy7432
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The engine is 2 years old and has had this issue from the beginning. In the beginning it would run for about 10 minutes before it would have the issue. The exhaust is side mounted and the fuel clunk is a felt clunk. The prop is a 16x6 as recommended in the manual. The fuel mixture is correct. I have replaced and gone over the fuel system for air leaks. If the engine is overheating is this how it would react? It only does this at higher RPM and when I here it begin to sputter I throttle back to low RPM and it I catch it right it does not stall. If it is an air leak or a clogged internal fuel filter is this the way it would react? Wouldn't it have trouble running as soon as it starts?
Old 12-04-2018, 11:29 AM
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speedracerntrixie
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With a partially blocked internal filter the engine will start up and run fine but can fuel starve at higher RPM. Your felt clunk will only work as a filter if you are using a 3 line system. You make no mention of any other filter so the evidence is even more in the direction of debris partially blocking th carbs internal filter. Still not much info to work with. As I said before, the more information you provide about your setup will get you more accurate answers. Here is a picture of what I consider a textbook fuel system. Large filter between the carb and the fill line, even the vent is filtered to prevent anything but air getting into the tank.
Old 12-04-2018, 12:28 PM
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Patient:
"Doctor it hurts when I do this"
Doctor:
"So don't do that"
You say you are using a 16 x 6 prop. Sounds under propped. Which in turn causes a tuning on the lean side.

What is the peak ground RPM you are getting? I don't like to see any more than 8400 on the ground for this engine. I bet your well above this.

Try a 17 x 6 wooden prop like the Xoar, find peak on the ground then richen the high untill it is about to lose RPM and fly it there (peak RPM will usually hold for about 1/4 of a turn on the high needle).

This is my guess.
Old 12-04-2018, 02:16 PM
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I agree about the prop being too small. Add some prop load with the much preferred 17-6 or even a 16-8 if you have clearance issues then make the filter and other checks suggested above then retune.

I had asked earlier about the engine being new or used and whether side or rear exhaust because the rear exhaust 20 can have some unique heat related problems the side exhaust version doesn't. A new engine that has never run properly will suggest different problems than an in service engine that develops problems during its life.

With your engine being run some but never being right since new, it is somewhere between a new engine and an in service one. It has had fuel run through it so all the fuel related suggestions you've received will apply. With the engine being two years old now, carb problems may have developed or been there since new, perhaps even defective. You don't know as the engine has never run correctly but the 16-6 prop may have contributed to the perception it didn't run or tune as expected. So how to get this engine running right? If the suggestions received so far don't resolve the problem and the engine seems in good mechanical condition (good compression, good reed action, etc.) a carb rebuild may be in order. If I had the engine here, I'd open, clean and inspect the carb and if I didn't find something wrong I'd set it aside and run the engine with a different known good carb. But you probably don't have that spare carb sitting around and probably don't want to buy one until you know there is a problem (or not) with the existing one. Moving on in no particular order, Ignition or ignition power issues (low voltage, bad switch, etc.) can also cause problems similar to what you are experiencing. Like with the carb, the easiest way to isolate an ignition problem is by running the engine with a known good ignition, if you have one on hand. Of course eliminate the easy to find possible problems like low battery voltage, bad wiring and switches. Again substitution with known good components is a great troubleshooting aid. Some later ignitions don't work well with 4 cell, 4.8V Nixx battery power and much prefer a 6V or greater power source. Again, something to consider. Some engines will do little more than idle and will pop, stutter and fart at higher power settings on 4.8V power where this was a normal power source in years past. At any rate, a few more things to consider.

Depending on your experience level and your desire to root out the problem, you might be better off just sending the engine to someone like Valley View RC for service. They can find and fix the problem at a reasonable cost and you can request an extended run test before they ship it back to you. If you go this route, be sure to include the ignition for testing.
Old 12-04-2018, 04:47 PM
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ahicks
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Please ignore the manual and put a bigger prop on your engine. I think you may be pleasantly surprised at a whole new (different) personality. WAY easier to tune for sure.
I would also pull that felt clunk to see how hard it is when I try to blow through it. If there's a lot of restriction (which is VERY possible!) it needs to be replaced.
Old 12-04-2018, 07:14 PM
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jimmy7432
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My set up is similar to the one pictured without the large fuel filter. I have ordered a fuel filter. Will try a larger prop. I thought a larger prop would do the opposite and cause it to overheat. My RPM on the ground has been 8300. One thing I was thinking is the carb is about 3/4 of an inch away from the fire wall. It was necessary to cut a hole in the fire wall for air flow. Its only 3/4 of an inch wide with the fuel tube coming through it. Maybe the hole needs to be slightly bigger.
Old 12-04-2018, 07:21 PM
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speedracerntrixie
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If your setup is like mine that I posted but without the filter then you have been running unfiltered fuel.
Old 12-04-2018, 08:26 PM
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Opinions for running an onboard, inline filter is a bit like asking what oil to run, etc. Wildly different opinions on what is right and wrong. I tend to believe it is like many things in this hobby ..... there are many ways of doing the same task right. I filter my fuel as it goes in the tank and for years, used no other filters. In the last year or so, I've gone to using in tank, clunk filters but overall have never had any problems with fuel contamination in the carbs. I usually inspect the carb screen once a year or so and rarely if ever find anything in the screen. A quick rinse and inspection and the carb goes back together. I've seen so many fuel filter problems on various equipments, I tend to not use one unless it is necessary. Use one if you must and if it makes you feel good but I prefer not to.
Old 12-04-2018, 08:48 PM
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speedracerntrixie
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I have seen a few guys take your approach and have issues. I have also seen the junk that my filters have collected. Could be a regional thing. I would not run any engine without an inline fuel filter. I can't think of any problems they would create other then not securing your fuel lines correctly.
Old 12-04-2018, 09:21 PM
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In 50+ years on my own airplanes, I have only seen one source of fuel contamination in an airplane (gas or glo) when the fuel going in the tank was clean and filtered. That source was crud getting into the tank via a muffler pressure line that we don't use on gassers. Carbon in the muffler would find its way to the tank and in this case, I used a Sullivan crap trap between the muffler and the tank. Other than that my tanks and carbs remain very clean. Most of my years, I've flown from grass fields that are often times anything but clean though our area is very humid in the summer. Maybe a more arid climate would be more prone to dirt / contamination problems but I simply don't know. I simply don't see the need for the additional complication of an inline filter.

I started using clunk filters after seeing how well they worked in chain saws and other equipment that is always working in a dirty environment. That and I switched to 3 line tanks that allow for their use where they just aren't compatible with a 2 line system I had used for a very long time. While I try to keep my saw tanks clean when refueling, they always seem to get some saw dust and crud in the tank. Also, I don't filter the fuel between the gas can and the saw tanks when refueling. The felt clunk filters seem to last forever in that environment and filter the fuel to the carb 100% with almost nothing getting to the screen. The saws also use Viton tubing which is a testament to the quality of that product.

This is truly a case of do what works for the individual. I'm not condemning other users in any way for their using a different system that works for them. This is a hobby after all!
Old 12-05-2018, 05:20 AM
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ahicks
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3 line system with felt clunk, no other filter on board for some time now, without issue.

3/4" carb clearance is fine. Even1/2 of that will work just as good.

Check, or just change that clunk!
Old 12-05-2018, 05:56 AM
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speedracerntrixie
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Iím running a felt clunk as well but as you can see I fill through the clunk so it is doing nothing as a filter. Just there to prevent bubbles. I however still do not feel a filter is a peice if mind device. I have seen too much debris collected in my filters. That being said Iím leaning towards the theory that here in CA we get the highest gas tax and the lowest quality gas.
Old 12-05-2018, 09:26 AM
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Originally Posted by jimmy7432 View Post
My set up is similar to the one pictured without the large fuel filter. I have ordered a fuel filter. Will try a larger prop. I thought a larger prop would do the opposite and cause it to overheat. My RPM on the ground has been 8300. One thing I was thinking is the carb is about 3/4 of an inch away from the fire wall. It was necessary to cut a hole in the fire wall for air flow. Its only 3/4 of an inch wide with the fuel tube coming through it. Maybe the hole needs to be slightly bigger.
When using a smaller prop the needle setting is leaner at any given RPM. Same RPM, air and less fuel and oil. The larger the load, the greater the needle setting. When the load becomes too high, the rpm is unable to reach optimum rpm for optimum torque. So yes more load creates more heat and power, but, there is more lube and fuel to balance.

Judging from some of the other responses you could still be forth coming with more details. Like :
what battery?
what oil?
what is your cooling air routing?

The more data detail, the better the group responses.
Old 12-05-2018, 12:33 PM
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Hmmm. Let me a guess here too. Because without more specifics that's what we all are doing is guessing based on practical experiences. So here's mine . I have seen 2 DLE 20's with mystery carb issues that required new carbs ,that's guess 1 . Guess 2 is replace the DLE spark plug with a real CM6 plug , we've all seen that issue . Guess 3 , the prop isn't balance and either the vibration is causing the ignition pickup sensor go erratic at high speed or vibration is killing the ignition switch and it drops/ reduces voltage to the ignition . Those are about the craziest guesses I've got , but just because they're crazy doesn't make them any less plausible... But seriously give us much more detail on battery , voltages , props used . How old the fuel is . Moon phase etc.
Old 12-06-2018, 08:37 AM
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I really want to see some pics.of your plane. Love the Citabria Pro!
Hopefully you can get that engine sorted out. Hate them dead stick crashes that most of us have experienced.
Old 12-08-2018, 03:13 PM
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Originally Posted by ahicks View Post
3 line system with felt clunk, no other filter on board for some time now, without issue.

3/4" carb clearance is fine. Even1/2 of that will work just as good.

Check, or just change that clunk!
I'm with the school of thought of a quality inline fuel filter from gas jug to fuel tank, a filtered clunk in a three line system and never had a problem since adopting this method.
Old 06-09-2019, 01:18 PM
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Originally Posted by jimmy7432 View Post
The engine is 2 years old and has had this issue from the beginning. In the beginning it would run for about 10 minutes before it would have the issue. The exhaust is side mounted and the fuel clunk is a felt clunk. The prop is a 16x6 as recommended in the manual. The fuel mixture is correct. I have replaced and gone over the fuel system for air leaks. If the engine is overheating is this how it would react? It only does this at higher RPM and when I here it begin to sputter I throttle back to low RPM and it I catch it right it does not stall. If it is an air leak or a clogged internal fuel filter is this the way it would react? Wouldn't it have trouble running as soon as it starts?
As Ahicks said, the problem may be related to air in the line.
You also mentioned that it happens only after at least 5 mins of flights.
In my opinion, a possible cause is the vibration of the engine that shakes the fuel and create foam. As the fuel level goes lower (after 5 mins of flight or more), you have less fuel in the tank and the problem starts.
I had the problem of air bubbles in the fuel line with glow engines despite the fact that the propeller was well balanced.
The way I solved it was mountain the tank on a layer of foam to eliminate vibration to the tank.
It worked well and my problem was solved!
Old 06-09-2019, 07:39 PM
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I've seen this problem at my local airfield on the same engine. The cause was the ignition module. It operated erratically after heating up and always resulted in the engine shutting off at full power. Replacing the unit fixed it.
Old 08-04-2019, 10:25 AM
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When my DLE-20RA eventually required full throttle to maintain a hover I realized
that I had a fuel flow problem. So, I did what most people say to do, "check the
screen". The macro photo uploaded here shows the Walbro fuel inlet screen with
debris and muck that could not have passed through the gas can screen and two
Sullivan Crap Trap filters on the way to the carb. The Crap Traps have 2 screens
each.

It appears that the stuff formed inside the carburetor. I just wanted to ask if
anyone knows whether it is caused by the ethanol gas alone or by the gas and the
kind of oil that is mixed with it. I use STIHL HP Ultra synthetic 2-cycle oil.
STIHL says it is biodegradable. I wonder what it biodegrades into.

By the way, I don't believe that the Walbro screen was clogged enough to cause
fuel starvation.
Old 08-05-2019, 10:08 AM
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That looks kinda like congealed oil or the residue from an old fuel mix that has started to separate. Yes certain mixes of fuel and oil can cause this sort of thing. Best fix seems to be using fuel that is as fresh as possible. Ethanol containing fuels seem more prone to this sort of problem because of their nature to absorb water from the air. You might seek out a source of Ethanol free fuel such as a marina or classic car fuel supplier.
Old 08-06-2019, 07:40 AM
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Truckracer, thank you for sharing your knowledge about the fuel that we use and thank you for suggesting the sources where ethanol free gasoline might be found. I know a gas model flier who owns a big boat and I know an old classic car restorer that I can ask. It appears that no pure gas is sold at the pump here but you can buy it in cans at a few places for prices like $24/gal or $83/5gal. Thats like glow fuel, WT..

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