i just finished building my four star with a husqvarna weed wacker engine....the radio works great but when the engine runs ALL the servos start to jump....HELP!!!!..lol

We need more info.
What radio system, what ignition on engine, where do you have your radio items placed, plastic connectors on engine pushrods?
Pictures will also help us help you.

its a jr xp652 radio with a jr r700 receiver and tower hobby brand high torque servos...it also has this... http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXJ776




thanks!!!!

I don't have any experiance with mag ignitions.
All my planes have had electronic ignitions.
I had a Fuji that the ignition blew so much RF, there was nothing I could do to stop it on a 72mhz radio.
I had to go to a 2.4 system.

I have seen lawn mower screw with 72mhz radios, just by getting with in a couple of feet of the radio.
I would think the mag ignition and that cable throttle linkage might act as an atenna and sending the RF right ot the radio.

Maybe some mag ignition guys can chime in here.

ok...i can change that if i have too

What is the wire running with the sparkplug wire?
The sparkplug cap is only a couple of inches away from that cable for the throttle.
RF is at the sparkplug and sparkplugcap, and your right on top of it with that metal throttle cable.

that is the kill switch wire

Yep, the metal cable for the throttle linkage has to go first. Then, if the spark plug wire is not shielded with a metal braid, you need to add one. I have had to do this before on magneto ignitions. You can carefully strip the insulation off of regular coaxial tv cable, then remove the copper braid and use that as a shield. Just ground it on ONE end; not both. For example ground it to the engine at either the spark plug end or the coil end, but not both. Finally, kill switch wires can also transmit rf interference. Keep yours as far from the radio and/or antenna as possible, and keep them short.

This all assumes that you are using a resistor spark plug. The plug you are using must have an "R" in the number, indicating that it is a resistor plug.

Do not fly it until you fix it. It will not "get better" in the air and you could well lose the airplane.

AV8TOR

ok..thanks...yeah..theres no way i'm flying it as is...lol

I have had several magneto spark engines that drove me nuts, until I completely wrapped the system in metal (foil/braid etc) and used shielded plug caps + resistor plugs and earthed the wrap on the engine.
Take care that there are no "leaks" in the wrap through which RF interference can escape.
No metal connection/rod/cable anywhere near any ignition/engine component going to, or even near to a radio component.
Keep ALL radio components and any leads connected to the radio system at least 8" away from

That never failed to work for me.

I agree with the recommendations to change the throttle linkage to plastic and crop all the extra wire off the kill switch or even do away with the kill switch and adjust the throttle to kill the motor. Most whacker conversions using mag will not fire unless spun up with an electric starter so the kill switch isn't needed when choking. If your motor by chance will fire by hand propping, then keep the kill switch for safety.

One other thing that hasn't been mentioned yet that I've experienced once is to keep the antenna wire away from any pull/pull wire rudder linkages. In that instance, the interference showed up while range checking and had the range reduced to an unacceptable level and simply re-routing the antenna wire to the top of the vertical stab reestablished a good range check.

ok..thanks guys...i'll try all of those[8D]

what should i use for a throttle cable..the only plastic ones i can find are for control surfaces and to big diameter

i unplugged the kill switch from the engine and everything works great...thanks

I would still do the other changes, is may bite you.

yeah...what should i use for the throttle pushrod??....i cant find any small enough diameter

Sullivan Gold-N-Rod or similar will work.

http://www3.towerhobbies.com/cgi-bin...?&I=LXFU92&P=7

ok..thanks!!

ok...so i took it out yesterday since everything was working and did a range check but now i found that it starts the interference again if it gets about 300ft away from me.....taking the kill switch off make it completely go away when its withing 200ft of me...i also took the metal throttle cable out and rerouted the antenna to the top of the fin, but it still does it??...where can i get a resistor plug if it doesnt have one in now???

200ft of uninterrupted radio range with your engine running is a very good distance, the important thing is that there should not be more than 10-15% difference in range with the engine off or with it running throughtout it's rev range.

Regarding the spark plug, what brand and model you are currently using.

Karol

i'm not sure....i got the husqvarna engine on ebay already converted...next time i get to where my plane is i'll check

what do you mean by 200 feet is good????....it will get alot further that that when its flying??? or is it less on the ground???


my question is why would the engine only cause interference at over 200ft now???

thanks!!!

Range check the plane with the tx antenna collapsed into the tx case. Engine off walk away from the plane and determine how far it is before the surfaces start jumping around from loss of signal. Of course this is with a radio that does not have a fail safe set to keep the surfaces at neutral where you can't tell what's happening. The have someone hold the plane and do the same test with the engine running. Check the difference in distance. 10-15% is the max loss that's acceptable. A ground range chek that consistently is good at 200' is a good range check, especially if it's the same engine off and engine running

If you're trying to do the range checks with the tx antenna extended and/or with the plane flying you need to better understand what is meant by the term range check. It is never, ever done in the air, and always with an antenna in it's least radiating state.

Any auto parts store has resistor plugs.

lol...i just did that...300+ feet with engine not running, 25 feet with it running...i'm going to get a resistor plug but i doubt that will do it...anything else

You might just surprise yourself.

Karol

i just ordered a resistor plug so i hope that will do it

There have been many, many cases where a non resistor plug left a plane completely unflyable and where replacing with a resistor plug fixed 100% of the problems. You should listen to some of the advice provided in this thread instead of being a cynic. Some of the people advising you have been flying gas for a long time and already experienced and learned from the problems you're having now. They have the knowledge you do not yet have.

Combine plug type with equipment types, condition, and installation methods and close to 95% of all "ignition" related issues are cured.