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Apr 21, 2019, 04:03 PM
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DLE 20ccra

I have a DLE 20cc ra gasser using redline two stroke oil 30:1
today was the first flight after bench running it for 3 hours or so
After the first flight I noticed the motor looked was discolored
And had burnt oil on to the fins and cylinder head
The flight performance was great no loss of power as I had upgraded my quarter scale space ARF Spacewalker from an OS 91 four stroke to a gas motor iím using red line two stroke oil 30 to 1 ratio
I need help to try to figure out what the problem is thanks
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Apr 21, 2019, 04:10 PM
Build a scale plane already!!!
scale_only's Avatar
My first thought was leaking from spark plug,,,,

Second thought is why didn't you open up the cowl vent holes in front of the engine,, it's like you're purposely blocking airflow??
Apr 21, 2019, 05:05 PM
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I figured this Cowl is like Swiss cheese I didn’t think I needed to open it up anymore
But it won’t hurt to cut it some more thanks
Apr 21, 2019, 05:12 PM
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More photos of the cowl
Apr 21, 2019, 05:55 PM
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sagomon's Avatar
you have plenty of exit area but you need some intake area in front of the engine .old rule of thumb was exit area was twice the size of incoming area.
Apr 21, 2019, 07:47 PM
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Thanks for the feedback and the good advice
Apr 21, 2019, 10:32 PM
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koppterX's Avatar
welcome fellow so caler…

first, why the three hours on the ground? there's no need to run an engine for more than a few minutes, if that, then go fly. the extended ground run is probably what caused the discoloration as the engine got hot. what likely saved it was the low ratio of 30:1. anyway, hope you get it sorted out. airflow over the front of the cylinder is a must.
Last edited by koppterX; Apr 22, 2019 at 09:11 AM.
Apr 22, 2019, 08:56 AM
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Agree on the Swiss cheeze. I'd be pretty tempted to buy a new cowl and start over again on the cooling holes.
Apr 22, 2019, 01:15 PM
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DGrant's Avatar
Originally Posted by koppterX
welcome fellow so calerÖ

first, why the three hours on the ground? there's no need to run an engine for more than a few minutes, if that, then go fly. the extended ground run is probably what caused the discoloration as the engine got hot. what likely saved it was the low ratio of 30:1. anyway, hope you get it sorted out. airflow over the front of the cylinder is a must.
I fully agree. All the nice cool is blocked by the cowling. The cowling intake area is supposed to duct the air into the fins, not around them. The way that cowl is cut, it blocks any direct air that's supposed to go through the fins on the engine.

And yes... it was probably the 30:1 ratio that preserved the engine somewhat. Aside from the discoloration of the fins/engine, I would wonder what that spark plug looks like as well. I'm not going to say 30:1 is right or wrong here, but myself and many others run Redline at 40:1 on everything, all engines, and even yard equipment. I've been running it like that for 15yrs with zero engine trouble... and the proper cooling/ducting in place is a big part of it as well.

So... I would also suggest getting a new cowling, studying how many of them are cut out, and get some air flowing through that engine compartment rather then around it. Good luck with it.
Apr 23, 2019, 10:50 AM
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I ordered a new cowl and Iím going to cut it out so I can get the proper airflow
The discolored fins started only after the first flight
I also checked the spark plug and it was loose and leaking
As for the 30:1 I was just going off of what was in the manual
Thank you all for the help
Apr 23, 2019, 12:02 PM
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Regarding the oil, there are a LOT of us running 30-32:1 in everything, from 10cc on up.

After years of messing around with ratios as lean as 100:1, in this hobby as well as others, there has been proof realized that there is NOTHING to be gained by these leaner mixtures. You are not going to be able to run a bigger prop, or a prop with more pitch, expect longer engine life, nothing.

The fact your engine survived as well as it did on the ratio you were running, tells it's own story....

Do as you wish.
May 03, 2019, 05:53 AM
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Gurgling sound on DLE 20cc RA

Hi there,
I'm quite newbies on gasser. As such, seeking for opinion on how to troubleshoot on 20cc DLE RA engine which making gurgling sounds while flying. Based on tx position when doing rpm measurement on the ground, the reading is around 3000 rpm till 5000 rpm when gurgling sounds appeared. Peak RPM is 8500 rpm. Idle Rpm is around 1750 rpm. Prop size is 16x6 and ratio of oil is 30:1.

LS and HS needle sligthly on rich side. Transition low throttle to high throttle seems to be no issued at all. However, when lower down tx stick from high to low , observed rpm was idling at 2000 rpm before it continue to drop to 1750 rpm (happened around 2 seconds) before the rpm stabilize. Is this reflecting the low neddle setting too rich?

Appreciate if you all can advise further on how to doing proper setting for DLE 20cc RA.

May 03, 2019, 07:06 AM
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That gurgling sound is something you might want to try and get used to. In flight, you might actually hear a slight miss. This is no fuel injected V-8 here. It's a single cylinder 2 stroke, running a butterfly carb designed a LONG time ago, and that's the way they run.

It is running rich for sure, but that's not necessarily a bad thing. For starters, it means your engine is not likely going to quit unexpectedly.

When new/not broken in yet, the engine is running kinda hot. It's using fuel to help cool it, so when new, it's requiring an extra richer mixture. As it breaks in, a few gallons of fuel down the road, you'll note that it's running extra rich, and can lean it a hair at a time until fully broken in. Keep it rich though. If you try to keep it right on the edge, you're not really gaining anything but the potential for trouble - quitting unexpectedly for instance.

In the air, at mid throttle settings and mid speeds, the gurgling will be most noticeable. It's about engine loading, as in it's not loaded much. More in kind of a cruise mode. If you think something is wrong, add some load. Give it some more throttle and pull the nose up into a climb. It should clear right out and go to work for you! Completely normal....

As far as that miss, somebody noticed a long time ago that if you open your spark plug gap up to something in the .025"-.026" range, often you can help that situation out big time. The wider gap burns this rich mixture a little easier for some reason. The trick is worth trying, not an internet myth.

Go fly, have fun, but don't be too critical of the way it sounds in mid range. You'll get used to it soon, and realize when it's doing that, it's just buzzing along, fat, dumb, and happy! -Al
May 03, 2019, 07:41 AM
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Thanks Al for your feedback. Will try to fly again tomorrow...

May 03, 2019, 08:22 AM
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Hi Al,
Photo of spark plug retrieved after flying session. What do you think? Thanks.


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