Hello,

I am fairly new to gas engines and I am having some issues. I have an evo 26gx that I can get to run at idol but nothing past that. I can advance the throttle and there is no change. I started with my needles at factory settings and adjusted the low end to see if I could get any response but no change other than harder to start. What do you guys think? Any help would be greatly appriciated.

so if you open throttle there is no increase in RPM, does the engine still run or does it die down?
if you "add" throttle response and there is no change of a running engine, it means that there is no actual opening further of the throttle plate, because either:
1. engine will accelerate with this action or
2. the engine will shut down with this action if it is too lean or too rich

That is correct. No rpm change when I advance the throttle. The engine does die when I reach half throttle and it changes over to the high end needle. I have adjusted the low end needle in both directions, rich and lean, to see if i can get a change and there was none. Only when I richened it up, it was harder to start. I know this is strange. That is why I am asking for help.

Note: Starting needle positions High 1 1/4 turn, Low 1 5/8 turn, Prop Xoar 18x6

you have way too much prop.
i have had same problem before til i figured that one out.
I have a Zenoah G36, (36 cc, which is 10 cc more engine than yours)
i put on a 18 x 8 zinger prop, and she would reach 7400 rpm.
then i put an 18 x 10 prop, and it would not transition up, i played with needles all day, til i figured out it was too much prop.
so i have a 4 stroke 1.25 CI, (or 20 cc) Saito engine, and i use a 16 x 6 prop.
you may want to use this prop:
since your engine is not broken in, you are putting too high a load on it/.

use the recommended 16 x 8 prop for the first 2 gallons you put thru her.
then switch to the 18 x 6

doubt that engine can swing an 18 x 8 once broken in.
i did check the evo web site specs for your engine.

try it out and tell me what happens.
i bet you that is problem.

I will try that. Thanks, I will let you know what happens.

Where did you get a Zenoah 36 ? No such animal that I know of..

Bingo!! that was it... Too much prop. I went to a 16x8 and it started and transitioned just fine. Now time to fine tune.

Thank you

sorry Antique, you are right, i have a Zenoah G38 and a Saito FG 36
this is called a "BRAIN FART" in a 42 year old.

18x6 should not be too much prop for that engine.
I have a couple of the same engine (ok - MVVS branded but otherwise the same engine) running 18/6 wood or similar load props. The one shown below on the WWRC profile plane (sorry about the cr*ppy photo, it's the only one of that plane I have on this computer) runs a standard "compact" muffler and spins a Vess 19a - it 3d's that happily around the place.

If your engine is not accelerating with that load, there is likely to be something else wrong. Is the engine new? Has it been sitting on a shelf somewhere for a while?

Set your high needle to max rpm then open it up about 1/16th of a turn (just as a starting point)
Set your low to the leanest it will go and let the engine run then open it up a very little at a time until you get a crisp transition. Then see what happens.

The 26 will run perfectly well using a 18x10 prop!!!! Just tune that carb well. Open the H needle till it will accept throttle. No big deal. I have run 20x8 props on that engine.

PS Steve,
You really sure there is an engine up front that plane? ROFLMAO

Thanks for the feed back guys. Orthobird I think you may have been dead on. Pe I was hoping to get your response as you are the guru on these engines. Although I have it running great on the 16x8 I beleive I still may need to move to a larger prop because it is turning 8100-8200 rpm's at full throttle. Is that to high? and what should my max operating temp be?

I have been enjoying an Evolution 26GX for about a year now and I am completely sold on the engine.

I use it on an 1800mm YAK 54 and the pairing is perfect.

I have been using an 18x8 wood prop on the engine from day 1 and the engine performs beautifully. It starts very easily (never used the choke) and transitions smoothly throughout the RPM range.

I have installed an inverted Bisson muffler and the combination is perfect.

It can idle all day long and diligently goes to WOT when the stick is pushed forward.

I liked the engine so much that I purchased a 40GX soon after I started using the 26.

mike

Originally Posted by pe reivers

PS Steve,
You really sure there is an engine up front that plane? ROFLMAO

LOL - I know exactly what you mean and I agree (terrible shot for sure). When people saw this plane come to the field for the first time, they all told me it was underpowered (even though they had never seen it in the air or even running - these are not a very common engine over here, nor ar profile planes) Most people put a DLE 30 on this particular airframe and run similar props to what I am running on the 26.

After they saw it fly they all wanted to have a fly of it because of how much fun it is. the enigne is the "SP" version and to make the install easier, I rotated the head 180 degrees to mve the plug to where it suited me, I have no idea how much the power curve changed by doing that but running a 3270 "compact" muffler and a 19A prop, it is a very nice power curve indeed for this plane. The needles are nto very close to the settings in the manual, By memory the low is in fact quite a bit in and the high is about 1/2 a turn open but don't quote me on that as my memory isn't all that good on such things - I just set the needles to where the engine works well and never really care much about "factory" settings on any engine.

The pic below shows it with the 3266 tuned pipe but I found that combination didn't suit that particular airframe and I wanted it a little quieter for one field I occassionally fly at so I changed it to the compact muffler

Jkimberly, if you engine is brand new, you need to break it in.
if you move it up to bigger prop, and it will not transition, this will more than likely signify your engine is losing compression.
may be a problem with rings, if it has any.
for now, use that prop and put 2 gallons fuel with 40 to 1 oil, ,after 2 gallons go thru, then move to 32 to 1.

Originally Posted by JKimberly

Thanks for the feed back guys. Orthobird I think you may have been dead on. Pe I was hoping to get your response as you are the guru on these engines. Although I have it running great on the 16x8 I beleive I still may need to move to a larger prop because it is turning 8100-8200 rpm's at full throttle. Is that to high? and what should my max operating temp be?

With a 16x8 your rpm should be way above 9000. What fuel and muffler are you running?
Did you try opening the high needle more? Or else get rid of fuel flow restrictions. (fuel lines, carb strainer, blocked needle jet etc etc.
Temperature measurements depend on measurement location. Topmost cooling rib against the cylinder wall, with sensor isolated from the airstream and in the prop blast leeway should see 135 to 150°C