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Idle Screw will not stay set on a 60C Carb.

Old 08-04-2014, 05:55 AM
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Default Idle Screw will not stay set on a 60C Carb.

I love OS Engines and never have a complaint on craftsmanship until today. I'm a very conservative modeler. Meaning I don't do anything extreme with my equipment. For that reason when I go out on a flight, most people would get bored watching me fly in ovals and a few loops and rolls.

The only time I remove my carburetor is when the engine will no longer run or idle reliably. Recently my OS 61 FX no longer would idle reliably at a little over 3000 RPM. After doing some trouble shooting (re adjusting the high and low end needles, changing the glow plug, and blowing the carburetor out with some canned air) I discovered that the Idle screw seemed a little loose. I removed it and found a small piece of something that looked like it was around the threads. I cleaned it off, and put it back in. I made sure it went in all the way, and then backed it out until the carburetor could just close. Then after a little carburetor adjustments to the High and Low end, it seemed like the engine was fixed. I flew one flight and landed. Not long after the landing I double checked the Idle RPMs. Then the engine died on it's own. After examining it again, I discovered that the Idle screw had come back out partway. I removed the carburetor and took it apart. When I completely removed the idle screw again, I found a very small, what appears to be a copper thread around the idle screw thread. I know that I didn't put that in there. It just isn't possible. Because the last time I cleaned that carburetor, I put each part in a small tub of Isopropyl Alcohol, rinsed each part off and put it together over a piece of paper towel on a clean table. It seems to me that the thread tolerance on either the idle screw or inside the carburetor is a little loose and maybe whatever this copper thread came out, the screw won't stay set due to engine vibration. As stated earlier I'm very careful whenever I do anything, and this screw almost never gets adjusted. In the picture I don't show the spring and it seems fine. But as you can see the foreign object/copper thread next to the idle screw.

When I looked at my old 40 SF Max engine I noticed that OS had the carburetor threads made different with some kind of insert/nut. This made more threads for the screw to go through.

I used a multimeter to do a continuity test on the foreign object. Doesn't seem to conduct electricity.

Last edited by gregoryshock; 08-04-2014 at 07:25 AM.
Old 08-04-2014, 07:48 AM
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If the fit of the idle adjusting screw is too loose, then you'll likely need a new carburetor body. It's not uncommon for the fit of this part to be a bit loose. The spring is what keeps it from moving. Sometimes, just pulling the spring a bit to lengthen it will do the trick to increase tension on the screw.

We cannot comment on the foreign object because we have no idea what it is or how it would have gotten into your engine. It's certainly not a part of the carb or engine.

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