Interference From Spark Ignition Motor - Help Please

[Madala]

I have installed a Zenoah 2 stroke spark ignition 26cc motor in a ARTF Cessna Skyline. Am using a JR Max 66 radio on 35 mhz but while the radio etc works fine with the motor NOT running, when the motor is running all of the servos start to act erratically.
I have the correct spark plug Champion RZ7C, there are no metal to metal moving parts, the RX and battery pack are far enough from the motor.
A "kill" switch is fitted. (These motors can bite real hard)
I intend to replace rudder and elevator aluminium arrow push rods with wood dowels and a suggestion is that I fit a capacitor between the motor casing and the negative of the battery pack.
Has anyone got some cure for the problem ?? There must be thousands of spark motors being flown out there but I have seen nothing about this sort of thing.

[Suky]

Madala, Im sorry I havent got a remedy. But I have exactly the same problem. I have a boat that I put longlines off the surf with. I have just brought a JR quattro radio set operating on 35mhz. It works fine without the engine running but once I start the engine have no control at all. It is powered by a 15HP Yamaha engine internally mounted. I got in contact with radio supplier and they said fit resistor spark plugs in the motor. I have purchased these but not fitted them at present. After reading your note I am not very confident. I will be very interested if you get any repies.

[Straick]

I don't know if they are the same as the larger 2 strokes, but have you checked to make sure that there is a capacitor across the breaker(if it has one). What might work(used it on a snowmobile that would kill the newer machines by just running near them) is to put a woven wire tube over the wire and make sure that it grounds to the motor. I'm not sure if it will work for you, but it will silence some of the RF noise that you are getting from the ignition system.
I'll be honest, I've never tried these on a small motor, but I did have my 72 Skidoo(2 stroke engine) fitted out with both so that it wouldn't kill newer machines with its RF noise.
Your other option, get a different radio that runs in a different frequency band so that you are away from the motors frequency.
Good luck.

[expo]

I've heard that a good PCM rx mounted well back from the engine and some metal in the firewall for interference block may solve the problem. I've also heard that running your antenna out the wing instead of the rear may help also.

I'm wondering if mounting the rx in a metal box may help also.

[Madala]

Thanks to you Guys who replied. I have been side-tracked by other more important domestic chores so very little progress with the plane so far. I am installing a JR PCM Rx and should have it all together next week. According to those who claim to know, PCM is the way to go but this is still no guarantee that the problem will be solved. A club member crashed his 1/4 Cub 4 times using a 2 stroke spark motor & PCM radio, then compared his plane with another which was identical in ALL respects except that he had wire in his wing struts. Removed them and the interference was gone. Seems like the wire caused harmonics in the radio signals resulting in the crashes. I have replaced the aluminium push rods with wood dowels, shortened servo leads as far as poss, sited the Rx as far down the fuselage as fingers will reach & re-routed the aerial outside, on top of the fuzz. I don't like routing an aerial along the wing. I lost a plane once because, I think it was at extreme range and the aerial was along the far side wing ie pointing away from the Tx. Thanx again chaps. Will report progress. I wonder why there is no comment from the hundreds of flyers who fly large spark motors. Do they read this stuff ??