ZDZ 40RV Problems

I test run it after the RTV application, no difference. Since I had the cowl off and easy access to the needles while it was running (the ZDZ's carb is way back and safe to adjust if you're careful) I noticed some interesting things. The lowspeed idle would adjust the mixture easily and I could then run it up as high as I could get it and the high speed needle did almost nothing at all. I could run it nearly in with no change, and nearly out with no change.

If I want to insure the high speed passages are clean, what's the best way to do it? I squirted some cleaning fluid into it when I had the carb all apart and watch it come out the holes. Is there a better way?

make sure your throttle butterfly is not set up backwards. This seems to happen a lot on ZDZ's.

Brad

I'm using a 20x10 on it.

The throttle plate cannot get turned wrong on the ZDZ40. I had a similar issue with mine. Disassembled carb and cleaned all the small passages with a very small piece of wire, then carb cleaner then air. Also turn the plate with the atmosphere hole so that it faces the rear of the plane and not forward, as it is from the factory. Could be pressure from the prop blast causing you a problem with the diaphragm. Hope this helps.

I have seen several people do a mod where they drill a hole in the diaphragm cover and silver solder a small piece of brass tubing in the hole. they then add a piece of fuel tubing which goes to another piece of tubing (curved) which is mounted on a convenient carb screw and points straight into the venturi. The idea is that the carb then senses the atmospheric pressure at the intake rather than a false reading it might otherwise get. I know this is confusing. If anyone knows of a link showing the process, please post it.

The tubing you are referring to goes back into the fuselage away from the cowling area that can get pressurized and hold the diaphragm in a locked position. The hole needs to see atmosphere pressure so the diaphragm can operate properly. Facing in the venturi would cause a different pressure from atmosphere and would probably cause all kinds of problems.

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I've seen them the other way more than the way you describe. Someone want to jump in here and explain? I'll look for a link.

I saw a link to a gizmo just like you described. He was selling those items, just unbolt your plate and put his on. He said they worked real good too.

In any event I might have it running again, will have to fly it and see how it does. For some reason my lowspeed idle needle needs to be turned out 2.5 turns now, it used to be less and was closer to 1.5 turns before.

The highspeed idle will adjust now like it's supposed to. One thing I noticed, my oil covering the bottom of the plane is back, I had though as it was decreasing that the breaking process was getting closer since the black goo was going away each time I flew, but in reality the mixture was getting leaner each time I flew.

I did take the carb apart again and found no blockages in the passages, and I did manage find one source of a rebuild kit at

I could find nobody around here locally that had stuff or could even order stuff for a Bing, few had even heard of them except on bikes.