Hello and thank you to anyone that can help.
i have completed my first gas build and it is a treehopper and I have installed a DLE 30 with Walbro carb and electric ignition. Yes I an a noob
I am using a Spektrum DX7 with spektum AR8000 received

I have the throttle servo mounted right behind the firewall. The Electric ignition is about 3 to 4 inches away and under the plywood that supports the servos and fuel tank and about 8 inches away from the recieved that is in the back section. I do have the recieved close to the battery but I do not think this is a issue as none of the other servos jitter or move. See picture below. The ign wire does run out the firewall next to the throttle servo and the throttle servo wire i have run above the plywood and as far to the other side as possible. It is next to some of the kill switch wires but not touching. I can start the engine and keep it at idle but if i give it any throttle it wants to jump to full throttle and back down or it kind of jitters around unless i keep it at the lowest thottle settings.
So where and I going wrong? I have tried to mess with some of the wires to see if one of them in the back makes it worse or better but so far no luck. I have thought to move the thottle servo back behind the gas tanks and move this up but it will still be about the same distance away from the ignition but it would get it away from the ign wire. Anyone have better ideas? Or should i just put in a huge electric motor and not fool with the gas?

Dlvsm<br type="_moz" />

here is the other photo

Are you a beginner? If so, who talked you into going gasoline power? It's a tad bit more complicated than both electric and way more complicated than glow fuel.

I am not into gas so I can't really help you but I'm sure someone here can help.

As far as switching from gas to electric - well, that could be jumping from the fryiing pan into the fire.

Good luck!

CGr

The pictures are not much help, where is the ignition module? Is it under the throttle servo? If so that would be a bad idea and I would prefer to put it well aft with long non metallic pushrod.

Your fuel system seems intensly over done and taking up far to much internal fuselage space.

John

Ok so did read that the kill switch can cause this so I went and removed this and plugged the battery right to the ign and it seems to be the same but now it fluctuates at low throttle not at mid or high now. I did also forget to mention that I do have a resistor on the transmitter. I also have a tach on the ign. and it is acting weird in that it keeps resetting and not always showing the rev's especially when I am starting the engine. not sure if this is related but another clue. Another annoying issue I am having is the only way to get the engine started is if I remove the plug and dump some gas in the engine. Otherwise is just does not seem to prime and get started. Not enjoying this engine so far but when it does run it sounds good, especially would sound good if I could adjust the mixture while it is running but I do not trust it to stay at any engine speed with the throttle jumping.

To CG I am kind of a beginner as I flew and crashed planes as a teenager that my Grandpa built. I have been flying small and medium foam airplanes now again for the last year and yes Glow is less complicated it is a lot more messy and I remember as a kid cleaning goo fom the side of myplane after every flight. So I built a big as plane and thought Gas would be easier. Huh...

DLVSM<br type="_moz" />

John,

Yes, the ignition is about 2 inches back and 1inch to the left under the big ass gas tank. Not right under the servo but as far away as I could get it. I agree that the gas tank is over done but I had the room and bought this before I decided to put the servo for the throttle in the front. Being cheap and not worring about weight I just moved it back and it is more inline with the CG. AS far as the throttle push rod it is metal but it is all plastic where it connect's to the carb so I thought this would be ok. No?

DLVSM<br type="_moz" />

Ok. Since I learned on glow power, cleanup is no big deal to me. Good luck with it.

CGr

A few things:
1) Where is the battery wire connecting to the ignition box routed? Is it parallel to any servo wires/extensions, or metal push rods?
If there is any RF leaking from the ignition box it will be traveling down the battery lead and the battery lead will act as an antenna as well. Keep the ignition battery as close to the ignition as you can and make sure the battery lead is away from and not running parallel to any wires or control rods.
2) What type of control do you have between the throttle servo and the throttle arm. Is there any metal to metal connection from the servo arm to the throttle arm? If you have a plastic servo and throttle arm you should be OK. If the arms are metal you would need nylon clevis or ball link,

Get a package of these chokes and take the throttle servo lead or extension and at the receiver end wrap the lead around the choke three times and secure getting the choke as close to the receiver as possible.www.horizonhobby.com/products/rf-filter-ring-style-2JRPA029

Also take that tachometer off as it's only to check/test the engine. You don't leave it in to fly.

Like I said, more complicated. Definitely not for beginners.

CGr

Having a servo within 10" of the spark plug or ignition coil is a bad idea. The windings from the servo pick up the pulse and transmit it directly to the receiver. EMI very possible. Use a plastic Sullivan rod or similar to operate the throttle andkeep theservos for throttle andchoke/smoke behind the fuel tank.The straight light-blue tubes in these images are Sullivan Gold-n-rods to servos 12" from the magneto of this model.

Anything metal that can vibrate against the engine can cause problems. No metal clevis on throttle or ignition. Use ball links and nylon control rod.

The spark plug cap not on all the way can also cause problems. It is also easy to rip the white insulator on the cap, allowing spark to jump from the center electrode to the outer shell.

Like I said, complex.

CGr

Since it's only the throttle servo giving you problems, have you tried a different servo? My first thought would be either a bad servo or vibration making that servo mess up since it's so close to the engine. The potentiometer in servos is the most vibration sensitive part in them, so if that servo is getting shaken it could be causing the pot to sense movement that isn't really there and then correct for it.

^^. Good point.

Jester,
Ok so if it is a Vibration issue and assuming the servo is fine ,as this is the second servo I tried, is there a particular servo that would be better suited for this location? Or am I just going to be much better off moving the Servo back away from the firewall where the vibration is not so bad or as viloent? Also if it is a vibration issue why doesn't it do it all the time or only at low end when I first add throttle from idle? When it gets above mid throttle it seems to be ok. I know that the vibration is worst at idle but gets better when I throttle up so I am not sure. If there is a Servo that is more immune to this let me know. Thanks again to everyone.

Dustin

the battery can act as an antenna for RF noise... I try to keep batteries Ignition and radio control separate. I don't want my radio close to the batteries if at all possible. Keep trying different layouts. I usually have the ignition battery far forward.

I have experience with many gas models... it is not that difficult. Stick with it.

Make sure your plug cap is on ALL THE WAY

Chokes in a 2.4 system....I personally wouldn't bother.

Stuff separated by a few inches? Again...whatever floats your boat.

I'd be looking for a loose connection or something vibration induced with the servo.

Metal to metal, while not a great idea, creates interference well below the frequencies 2.4 operates at.

Had a similar problem and replaced the ignition module. Problem solved. Went back to glow eventually.

Dl, you have lots of problems with that installation and not enough detail in the images to see exactly what they are. Follow this advise from Futaba's website. Dan

Guidelines for setting up gasoline engine models.
All ignition equipment, including an electronic kill switch, must be mounted at least 12", and preferably 14", away from all radio equipment, including throttle servos, etc. Ignition kill switch should always be on opposite side of fuselage from radio kill switch. All pushrods going to anything related to the engine must be non-conductive (just nonmetal clevises is not sufficient).

To the OP.
A lot of folks here trying to help you but you don't seem to be answering many questions.posed to you.
I'm not as anal as some folks with their installations but looking at your pics you really need to clean up the install. Get the wires separated power and servos and bundled together and secured. Ignition battery mounted close to the ignition, no metal to metal control rods,etc...etc...
As far as the servo being too close, I have an ultrastick with a chicom 40cc engine and ignition. Ignition is on the firewall and the standard size case servo is about 4" away and wires are run on opposite sides of the fuse. I have no servo problems.

Read this http://www.rcuniverse.com/forum/m_8673009/tm.htmread it again and again and again. Move your ignition to the front of the firewall, pad it; pad it good. get rid of the big A tank; not needed go to 10oz will fly 20min on that. Lots of old information out there regarding setups before 2.4 came along, but the information in the sticky will get you going in the right direction

If it is a 2.4 system I have to disagree. 2.4GHZ is nearly immune to such interference. If it is a 72MHz system maybe so.
I have been flying RC aircraft for about 70 years. I have NEVER had an interference problem that affected only one servo There has to be something wrong with that servo.
I am currently trying to fly an old Goldberg Ultimate with 26CC gas engine. That engine makes all servos jitter. I had to put in a Hyde soft mount to quiet things down. Maybe thats your answer. It will cost you a bit though

Is there anyone in your area who is familiar with gassers?  Find as many nearby clubs as possible and stop by with your setup. It's very hard doing it long-distance.</p>

I agree that it sounds like ignition interference. Search the forums for correct installation technique. It ain't rocket science, but you need to understand the basics of routing wires and keeping components separate. I always put a shielded cap on gasser plugs, gets rid of the worst interference.</p>

" Metal to metal, while not a great idea, creates interference well below the frequencies 2.4 operates at."</p>

I have to disagree. 2.4 can be swamped, like any other frequency. Just not as easily as 72 Mhz  or others. Remember when PCM was going to cure all?</p>

Feel free to disagree, I have no problem with that.

But I stand by my statement that 2.4 wont be wiped out by a couple of pieces of metal vibrating.

To Dlvsm,
Keep that ignition module and receiver as far apart as you can.  Put a choke on the ignition wire to the receiver.  Eliminate as much metal to metal contact as you can.  Check your servo.

But, most importantly, congratulations on your first gasser.  Before you know it you will be flying 33% and then 40% and then.............

Just my opinion, gas is much easier.  I fly gas giant scale, glow, electric and turbine.  Don't let anyone discourage you!

Good luck!