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90LX quitting while opening throttle past 3/4

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Old 06-18-2010, 08:20 PM
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BillO
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Default 90LX quitting while opening throttle past 3/4

I had my 90LX on the test stand for a little run. It's been since last summer that I ran it. It started fine. Idles fine. When I throttle up, once I get to about 3/4 open, it suddenly quits. It has had no lean runs. The plug is fine.
Suggestions?

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Old 06-30-2010, 08:42 AM
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Default RE: 90LX quitting while opening throttle past 3/4

Bill,

I think Dub and I chased this in email with you. How did you make out ?

But just in summary..... a few things could be happening it could be going rich to quit, or lean to quit. Might be the plug too

If for some reason you turned the low-speed mixture needle from its factory position, that is one cause. That is more of a low/mid speed mixture adjustment but if turned too far from position it will mess up the transition to the point where it is difficult, with any needle setting, to get it to transition to the top end.

Clearly, the other things to check - ensure there are no holes/kinks in the fuel lines. No bits/particles possibly in the fuel system or carb ( I found a tiny piece of silicone in one engine two weeks ago ... drove me nuts till i flushed it out of the spraybar).

A bad glowplug will light, fire and run, but can blow out when it tries to go to full throttle. Worth a quick plug change to eliminate that variable.

Let me know how things are going.
Bob
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Old 06-30-2010, 09:37 AM
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Default RE: 90LX quitting while opening throttle past 3/4

Thanks for the reply, Bob. I tried to look back in the RCU archives if a similar problem had been discussed, but that system did not work the several times on various days for me. I have not asked for help on this problem previously.
I did buy the engine used last summer. It was a trustworthy source of sale, so when I was told it had very little time on it and it was not abused, I believe it. It came to me looking as new. The seller said he broke it in on his stand, and then installed it, but it was too much engine for his warplane. He has other Jetts from Dub.

I did try another plug with the same result.
The fuel is 15%, not contaminated and filtered. I'll try with a new filter.
There are no kinks or holes in the fuel lines.
There has been no foaming on the engine stand.
The NV is the supplied one. I dug out the sheet that came with this engine. It does not address the 90LX specifically, but in it suggests the position of the low end screw. I have not touched it, and it appears to be in about the flush position. The other day I did screw in the NV all the way, and found it to be about 2 3/4 turns out. The sheet suggests 4 turns as a starting point. I will start over at that setting. Maybe that's all there is to this problem. I haven't been going out to the field, so this engine on the stand for now is not a pressing issue, but of course I want it up in the air soon. I want to hear it up in the air.

Again, thanks for the reply.
Warmest,
BillO
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Old 07-08-2010, 10:34 AM
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Default RE: 90LX quitting while opening throttle past 3/4

Thought I might follow up ...... any good starting over with the low speed mixture?

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Old 07-08-2010, 03:44 PM
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Default RE: 90LX quitting while opening throttle past 3/4

Hi Bob,
Many thanks for your follow-up. I have had no real chanceto work on it yet, even in my own backyard.
There's been one thing after another slowing me down, and on the decent days, I've had to do yardwork (depending on the weather), or errands for an elder in the family I go over and care for, or sometimes, just too plain lazy ot get at it.

I will follow-up here when / if I straighten it out.

Thanks again.
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