I have a zenoah G26 that for some reason i cant make stay idleing. The engine will run great on the ground, runs great anything above an idle. But almost every time you go from wide open to idle in the air only the engine dies or either goes what sounds like extremly rich ( it will be real slugish and then pick up ). And also when you go to get the plane when it dead sticks there is fuel coming out of the vent tube.

Here is what i have done to try to fix the problem. Took the tank out and check to make sure vent was correct. No problem there. Put a new diaphram in on the needle and seat side of the carb. That was no help. Welded a copper tube to the diaphram cover to make sure there was no change in barametric pressure. Still no help. I have tried every size prop from a 16x8 to 18x6 wich the engine is suppost to turn all of them.

The engine is new and has about one gallon of gas threw it. It is mounted to a Ultra stick. If anyone can offer any help on this it would be greatly appreciated. I am tired of trying to adjust this thing and fiddling with it. Oh and also i have started over with needle adjustments a few times ( started back at factory specs) and turned the needles very little at a time. PLease help !!!!



Chad

Chad, Sounds like your using muffler pressure to the tank. If you are don't. No need to pressurize the tank, the engine has a fuel pump.

I am not using muffler pressure. Let me also say this i have several gas planes and have experience with gas , no expert but i do know them. Any other sugestions ?


Chad

How low are you trying to idle it?
You might have an ignition problem. If your ignition system is not up to what it should be it would show up on idle assuming you are using the magneto that came with it.

There's one thing you did not mention and that is a extension pipe on you carb inlet. Some people call the velocity stacks. Most of them have a angle cut into the entrance. Most of them can be rotated to make the entrance somewhat face one direction or the other to get the engine to run just right. Mine all work with it towards the front.

My opinion is that your idle mixture is rich. the engine is idling OK for you on the ground but up in the air, it has idled for a longer period or your carb is inside a cowl that is pressurized by incoming air?

Enjoy,

Jim

If you installed the brown intake and modified the carb for the install you may have the butterlfy backwards. Looking in the carb from the intake side you should see the threads of the butterfly screw. If you see the head of the screw the butteryfly is working backwards, just turn it around.

Dirtybird, what kinda ignition problem are you talking about ? What should i look for ?


I do have a velocity stack on it. but it will only turn 2 ways and i have tried it both ways. The engine will idle on the ground for long periods and still transition up very well.

I'am only idling it as low as needed ( i idle it up till the plane wants to move forward a little on the ground). Actually i would like for it to idle lower but i'am idling it up to maybe keep it idling ( doesnt work ) . Thanks for the input guys , i will look at all of these sugestions!

Chad

Ignition problem possibilities.
1) Bad spark plug.
2) Poor fitting spark plug cap or bad high tension lead.
3) Bad coil
4) too large of gap between pick up and flywheel
5) I don't know if your unit uses a capacitor but in the old days with points this was usually the trouble

About the only way you can check these items is by replacement except item 4.

I had basically the same problem with a G26---would idle all day on the ground---ran great in the air under load---but on a long landing approach with throttle back to idle & the prop "Windmilling" the engine above idle RPM's it would quit every time at just about touchdown! (although no raw fuel out the vent)---restart it & it would idle all day---the answer for mine was to richen the low speed mixture, I guess not enough fuel in the circuit to handle the "Windmilling"---for what it's worth..........

Well i belive i got it fixed , i did about 30 take off and landings and no dead sticks.


This morning i rebuilt the pump side of the carberator. I ran it after this and found that the fuel tank was absorbing alot of the vibration from the motor, i put foam around and under the tank to help with this ( not sure fuel foam will afect a gas like it will a glow). I checked the spark plug and cleaned it.

Went back out to the feild this afternoon. The motor ran worse and had no power []. I did not do must adjusting to the carb after all this work on it so i went back to factory starting specs. Whalla the engine preformed perfectly with just a few tweeks for final adjustment.

I sure do appreciate all the help you guys put in. I believe with you all's help the motor is now preforming properly. However i'am not real sure as exaclty what fixed the problem. thanks everyone !

Chad