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Old 06-12-2008, 08:16 PM   #1
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30 size help

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the engine is surging during hover, as if the throtle servo is glithcing, but only the throtle, the rest are fine.

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Old 06-12-2008, 08:34 PM   #2
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Re: 30 size help

Either you have some fine dirt particles in your needle assembly, a dirty filter, or your
low speed is set too lean. Open it 1/8 turn with a jeweller screwdriver and try again.
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Old 06-13-2008, 05:43 AM   #3
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Re: 30 size help


Casset.............. low speed is set too lean........... I myself am asking about this solution . When the caburater is full open , I thought that the low speed needle has very little effect on the RPM . I can understand this in the MID range area .

If I was to suggest what was wrong ( and I m no Gurru ) it would be , TANK , FUEL LINES ( air intake ) , OBSTRUCTION OF MAIN NEEDLE VALVE

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Old 06-13-2008, 09:13 AM   #4
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Re: 30 size help

Yes that is correct. Cracked lines can cause a lean run also. So start with that. I set the low speed by putting a piece of tube on the carb and throttle almost off. You should hear
tiny amount of air until it is closed.
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Old 06-13-2008, 11:48 AM   #5
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Re: 30 size help

"the engine is surging during hover"...for me the key word is HOVER....not wide open in a climb.

You did not say what heli, engine, fuel, glow plug, muffler...these can all effect the engine set-up....relative also to the throttle curve matching the pitch curve.

But from the quoted statement above.

1 - Are you sure your throttle servo isn't glitching - have a friend watch it while you hover to insure it isn't.

2 - As the idle screw has a good deal of effect on most carbs at the close to half open setting of the throttle barrel of the carb in the hover, I would suspect that the idle screw is set too lean or too rich. If there is no hesitations (loading up) as you throttle up then it is too lean. Start leaning the idle screw out 1/16 of a turn at a time.

3 - If it does it at full tank, then fuel line leak is not as big a possibility, as all lines are immersed in the fuel. At full tank this may only be a possibility if the fuel line walls are deteriorated or too thin causing them to colapse inward when the engine tries to draw fuel.
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Old 06-13-2008, 10:03 PM   #6
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Re: 30 size help

check to see if your fuel pickup line is to long and the clunk is getting sucked to the rear of the tank and cutting off fuel draw.
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