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Old Dec 26, 2012, 09:19 AM
Meramec Mike
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Throttle programing issue

I have a DLE 20cc engine I mounted on a SBach profile plane and I have everything ready to go except one issue that I can't figure out, When running the engine and throttle up and then back down to the idle position the engine stays at a high idle until I tap the throttle cut button then it goes down to the idle position, there is no binding with the control arm it moves freely by hand, I tried trimming the idle down but that doesn't help the high idle issue when backing down the throttle does anyone have any idea's on how to fix this?
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Old Dec 26, 2012, 10:16 AM
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You may want to check your servo for a broken or chipped tooth on the gears. If there is no binding in the linkage that's the only reason I can think of that it could be.
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Old Dec 26, 2012, 11:26 AM
Meramec Mike
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rjstrickjr,,Thanks for the reply it's a new servo but I will check it out and see, I just thought of something that could possibly have an effect on this ,this is my first gasser and when installing the engine I read about disabling the throttle spring so I removed it so it wouldn't have a chance to catch anything in flight but then I read on a forum somewhere later that you shouldn't remove the spring just release it, do you think this could cause this problem?
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Old Dec 26, 2012, 04:39 PM
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The spring helps keep the throttle plate centered so maybe that could contribute to the problem. Look for any play in the linkage, or the servo doesn't center the same each time. Do you have the low end point set with the trim at the bottom and the throttle completely closed?

Have you tried idling down then waiting for maybe 30 sec. to see if the RPM drops? Some engines take a little while to reach idle RPM.
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Old Dec 26, 2012, 06:03 PM
Meramec Mike
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@600bob, the servo seems to be perfect it stops in the same place every time and you asked if the idle would eventually drop if I wait and it does but it takes quite a while and if I tap the throttle cut button it drops right away,it just seems to me that it would be hard to land with the idle at 2200 rpm's. There is a little side to side play in the throttle barrel so this weekend when I get time I will experiment by holding the throttle to one side as I control it and see if that makes a difference.
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Old Dec 26, 2012, 08:16 PM
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You might be a tad lean on the idle and maybe even lean on the top. If the engine is warmer than normal it takes a bit for the idle to come to normal idle speed.

Ken
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Old Dec 27, 2012, 04:33 AM
Meramec Mike
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@ Ken ,OK thanks for the reply I will also give that a go this weekend.That's what I love about these forums if you have a problem you will get several ideas and usually one of them is correct.
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Old Dec 27, 2012, 05:34 AM
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Actually, I was thinking it might be a tad rich...
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Old Dec 27, 2012, 11:22 AM
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what does the servo do when you retard the throttle? does it just sit there or does it retard and the engine stay at high RPM...and do you have the muffler installed? If the servo does not retard with the throttle stick then you have a radio program or radio issue...if the servo retracts but the idle stays high then you have an engine issue...muffler or more likely mixture
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Old Dec 27, 2012, 08:33 PM
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Originally Posted by JeffinTD View Post
Actually, I was thinking it might be a tad rich...
Yep, that will cause it to "hang" before returning to idle. My DLE did that. Common error people have is setting the HS too rich. It is a carryover from nitro habits I guess.
We are assuming that the servo is returning as the stick is lowered.
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Old Dec 28, 2012, 02:27 AM
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I'd also be looking for play in the throttle linkage. What happens if you put a little finger pressure on the throttle arm (if you can do so safely)?

With some slop, the throttle arm might end up in two slightly different spots when the servo goes to idle from higher throttle as opposed to going to idle from the kill position.
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Old Dec 28, 2012, 07:04 AM
Meramec Mike
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@fokker the servo is fine I have the needle settings at factory and it runs smooth and a good transition from low rpm to high so I havn't messed with them much but I will give that a try this weekend.
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Old Dec 28, 2012, 07:07 AM
Meramec Mike
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@jeffin ,that was the first thing I changed because I had a Z bend at the throttle and it had a small amount of play so I bought a ball connector set up and now there is no play in the linkage.
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Old Dec 28, 2012, 06:47 PM
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I have a DLE 20 and I have also struggled to get a reliable low idle. I now have it returning to idle at ~ 1800 rpm every time, but I had to have absolutely no play in the throtle linkage and a high quality servo that has zero deadband.
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Old Dec 28, 2012, 08:40 PM
probro 2567
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Midlothian,VA
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Quote:
Originally Posted by Mgblunt View Post
I have a DLE 20cc engine I mounted on a SBach profile plane and I have everything ready to go except one issue that I can't figure out, When running the engine and throttle up and then back down to the idle position the engine stays at a high idle until I tap the throttle cut button then it goes down to the idle position, there is no binding with the control arm it moves freely by hand, I tried trimming the idle down but that doesn't help the high idle issue when backing down the throttle does anyone have any idea's on how to fix this?
Possibly you need to set your end points. If you tap your throttle cut button it should cut the throttle so that the butterfly in the carb fully closes and cuts the engine off. Disconnect your linkage and manually operate the throttle with the engine running, SAFELY. Pull the throttle all the way closed and it should cut the engine off. If it doesn't then you might have an air leak somewhere or incorrect needle settings. If it does cut off then servo adjustments are needed. If you havn't already reinstall that throttle spring. Without it it can cause an air leak and possibly cause the throttle to not fully close. The spring acts as a shim/spacer for the throttle shaft. Also remove the idle set screw on the side of the carb, it's not needed. The servo will set the idle.
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Last edited by kwj48; Dec 28, 2012 at 08:57 PM.
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