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25FX tuning problem?

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Old 06-07-2012, 07:05 PM
  #1
mikeh251
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Default 25FX tuning problem?

I have several OS engines (25LA, 40SF, two 46AX's, 55AX) and now, a 25FX. I have never had any problems breaking in and tuning any of them until now. I have it running good now, but the thing that I don't understand is why I have ended up with both needles at only about 3/4 turn out? The book says the low end should start at 1and 1/2 turns out. I am all the way down to 3/4 turn out and it may need a little less! The main is at 3/4 to 7/8 turn out. All my other motors vary from 1and 1/4 out to almost 2 turns out. The other motors only ever needed a slight twist one way or the other for the low end. I have tried new plugs, fuel tanks, fuels, tank locations, props, spinners etc. I finally got it to run by going way beyond what I consider to be normal carb leaning. Anyone out there have any 25FX and if so, where abouts are your settings at? I am using Omega 10% nitro with has a castor/syn mix. 6oz tank 9x5 apc prop and 2" plastic spinner. I think it is collecting fuel in crankcase at idle making it rich in transition? Or its getting in from muffler? I notice it runs in reverse more often that not on startup. My other motors usually run backwards also, but only when cold and a full tank and primed. Once warmed up they rarely do it. Would removing the baffle help if this is the case? My next test is to start all over with run in as I noticed that this motor revs much higher than my others. I can let it sream for 15 seconds and lay my hand right on the motor/muffler whatever. Its not even hot at all. So now i'm going to make more extra castor fuel and go thru run in procedure again but this time let it sing some more. Maybe I was over cautious the first time? Then I'll go back to the regular fuel and see if the settings are still so out of whack. Or, are they really?
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Old 06-08-2012, 02:28 AM
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Default RE: 25FX tuning problem?


Quote:
ORIGINAL: mikeh251

I think it is collecting fuel in crankcase at idle making it rich in transition? Or its getting in from muffler? I notice it runs in reverse more often that not on startup. My other motors usually run backwards also, but only when cold and a full tank and primed. Once warmed up they rarely do it.
There is a lot here...but sounds to me like your tank position may be high relative to the location of the carb.
Tom
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Old 06-08-2012, 03:00 AM
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mikeh251
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Default RE: 25FX tuning problem?

I have had the fuel tank everywhere from underneath the plane to up on top of the plane. More than one tank, too.And, of course also in the normal spot of inside the plane where it now is. I have flown this plane and tank many times with the 25la motor. Main needle on that was about 1-1/4 out. Never touched low end on that particular motor. Just swapped out the la for a new FX. Cant understand why I had to move the needles so far away from starting points.
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Old 06-08-2012, 04:04 AM
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Default RE: 25FX tuning problem?

I have guys at our field that are exactly like you......I spend 10 minutes setting their motors for them, correcting all kinds of problems, like too lean, too rich, or won't run a full tank.

The next week, there they are, messing with the same engine that won't run. I ask them what they've done since I set it up for them? The answers always vary, but are usually the same..." Well the book says 1 1/2 turns out, and you set it at 2 turns out"...or..." I thought that maybe I should change the oil content, because..blah...blah....blah.......
They can't resist tinkering with stuff........once it works, leave it alone!!

In other words...if YOU make a correction, fix 1 thing to see if it solves the problem...and start with the simple stuff first, SETTINGS!!! Leave your tank where it belongs, don't go adding oil to your fuel.....it changes everything!!!

Like we used to say in the Navy..........Turns the sweat pumps off, and Don't sweat the small stuff!!
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Old 06-08-2012, 04:54 AM
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Default RE: 25FX tuning problem?

Yes you said you have had the tank on the top of the airplane and on the the bottom but you really have not noted and ignored a critical question: Is the Engine mounted Inverted? If so what is the relationship of the tanks centerline to the spraybar in carburators venturi? This relationship is carefully spelled out in the engine information that comes with it.

John
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Old 06-08-2012, 04:59 AM
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mikeh251
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Default RE: 25FX tuning problem?

Ha ha, I really like your post and I agree with you!!! I really am not normally one of those guys though. Seriously, I never touch my carbs once they are set. If it needs more than 2 clicks either way on the main, I know it is something else that is wrong. I fly several times a week and have not had to ever adjust any of the motors I mentioned. No deadsticks, no problems. I keep records of where the needles are set when I get the motor broke in just in case I may need to know, thats how I know where they are all at. As for the oil, just following the OS instructions for break in procedure. I did everything by their book and am curious as to why this motor needs to be set so far away from normal? With everything, including fuel, normal? It took a long time and all of the tests (done like you suggest, one thing at a time) for me to get to where it is. I couldn't believe that the low end could possibly need to be turned in by 360 degrees and kept trying other things. All the other motors only need a little 1/8 turn, or none at all. When was the last time you took 10 minutes to set up someones carb and handed it back to them after turning in the low end in 360 degrees? and the main at a little more than a half a turn out from closed? And, if so, did it happen to be an OS 25FX? Thats all my question is. all the other stuff is simply posted for someone who was maybe considering posting something I have already done.
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Old 06-08-2012, 05:41 AM
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Default RE: 25FX tuning problem?


Quote:
ORIGINAL: mikeh251

Ha ha, I really like your post and I agree with you!!!
When was the last time you took 10 minutes to set up someones carb and handed it back to them after turning in the low end in 360 degrees? and the main at a little more than a half a turn out from closed? And, if so, did it happen to be an OS 25FX? Thats all my question is. all the other stuff is simply posted for someone who was maybe considering posting something I have already done.
Mike;

I can't answer that question, because I don't care where the needles sit! I only care about how that engine sounds, and how it reacts to my changes!

Each engine is different.....each engine reacts differently to different fuels, altitudes where you fly, grade of castor in your fuel...dozens of different factors........therefor the needles cannot be exactly the same on each engine, and I think it's silly to keep a record of it, or to even worry about it!!

Just set it, and go fly!!!
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Old 06-08-2012, 05:57 AM
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Default RE: 25FX tuning problem?

The tolerances on RC engines aren't that tight, especially on something like a needle valve. So you happened to get one that's a little loose and has to be turned in more than usual. It's either that or you somehow have more fuel pressure at the carb than we normally do (not likely since you say your LA engine had normal settings). If this is your first .25 FX it may be that the factory setting on that particular run of engines is particularly rich. As said above, if the engine runs right there's no need to worry about it.
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Old 06-08-2012, 07:38 AM
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Default RE: 25FX tuning problem?

Hi!
Agree fully!
I have been flying R/C for 36 years ,competing in pylonracing mostly but also in scale and combat and in CL Combat. Never have I kept a log of how the needles on my engines are set!
The important thing is just to listen to how the engine sounds and set the needles accordingly! You do this in racing and you do it in sport flying!
Forget about how many turns you have on the needles. That's not important!
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Old 06-08-2012, 08:06 AM
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Default RE: 25FX tuning problem?

The FX series and specifially the 25FX was and still is a great engine and at one point I had accumulated 16 of the the 25FX's. Almost all used on multi engine ships clear up to six engines on one.

You asked a question and still have not disclosed what engine mounting orientation you used. If you used an inverted mount for the first time with out paying attention to the tank to spray bar relationship The symtoms you described are very, very common.

Many arfs that are inverted mounts make it difficult to maintain that all important relationship of the tank to the spraybar or jet.

John
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Old 06-08-2012, 09:42 AM
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Default RE: 25FX tuning problem?


Quote:
ORIGINAL: tomfiorentino


Quote:
ORIGINAL: mikeh251

I think it is collecting fuel in crankcase at idle making it rich in transition? Or its getting in from muffler? I notice it runs in reverse more often that not on startup. My other motors usually run backwards also, but only when cold and a full tank and primed. Once warmed up they rarely do it.
There is a lot here...but sounds to me like your tank position may be high relative to the location of the carb.
Tom
1. Is it running good or not? I agree with the set it and forget it comments, but I didn't think it was running good (ie. fuel collecting in crank, rich in transition, running backwards). All those symptoms, in my opinion, point to surplus fuel despite the fact that you have the needles turned way in. So that begs the question of tank position.

2. The comments on the engine mounted inverted are right on the mark! The tank location may be suitable for upright, but not inverted. Im sure John can help you with that...please let us know and we can give you more direct feedback.

Good luck with it.

Tom

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Old 06-08-2012, 03:03 PM
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mikeh251
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Default RE: 25FX tuning problem?


Quote:
ORIGINAL: RC MANIAC119


Quote:
ORIGINAL: mikeh251

Ha ha, I really like your post and I agree with you!!!
When was the last time you took 10 minutes to set up someones carb and handed it back to them after turning in the low end in 360 degrees? and the main at a little more than a half a turn out from closed? And, if so, did it happen to be an OS 25FX? Thats all my question is. all the other stuff is simply posted for someone who was maybe considering posting something I have already done.
Mike;

I can't answer that question, because I don't care where the needles sit! I only care about how that engine sounds, and how it reacts to my changes!

Each engine is different.....each engine reacts differently to different fuels, altitudes where you fly, grade of castor in your fuel...dozens of different factors........therefor the needles cannot be exactly the same on each engine, and I think it's silly to keep a record of it, or to even worry about it!!

Just set it, and go fly!!!
Were you born an *******, or do you just react to people that way?
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Old 06-08-2012, 03:19 PM
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Default RE: 25FX tuning problem?

Wow! You were asked at least twice if the engine was mounted inverted or not and still no answer, just a derogitory comment on how someone was born. Is it a secret about the engines orientation?
I have to agree with the "how many turns is it" response. What matters is if the engine runs where set. If inverted I would say hsn probably a little farther in than when upright. I always adjust my engines by sound, half turn out, 1 1/2, or 6 turns out, doesn't matter. Tune for maximum performance and then fly.
I understand you can be frustrated if it is not working right but from what I have read here you are just concerned about where the neddles are set rather that how it is running.
Good luck to you either way.

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Old 06-08-2012, 03:40 PM
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Default RE: 25FX tuning problem?

I have some of these engines. The 25fx is very powerful but have a design weakness. This weakness is in the needle base, the little hole in the base trends to deform easily. Give a look with a magnifier an see if is perfectly round. If not, you should to change the needle base in order to correct this issue.

Javier
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Old 06-08-2012, 05:16 PM
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Default RE: 25FX tuning problem?

Nicely stated Pamster.
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Old 06-08-2012, 06:01 PM
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Default RE: 25FX tuning problem?


Quote:
ORIGINAL: mikeh251


Quote:
ORIGINAL: RC MANIAC119


Quote:
ORIGINAL: mikeh251

Ha ha, I really like your post and I agree with you!!!
When was the last time you took 10 minutes to set up someones carb and handed it back to them after turning in the low end in 360 degrees? and the main at a little more than a half a turn out from closed? And, if so, did it happen to be an OS 25FX? Thats all my question is. all the other stuff is simply posted for someone who was maybe considering posting something I have already done.
Mike;

I can't answer that question, because I don't care where the needles sit! I only care about how that engine sounds, and how it reacts to my changes!

Each engine is different.....each engine reacts differently to different fuels, altitudes where you fly, grade of castor in your fuel...dozens of different factors........therefor the needles cannot be exactly the same on each engine, and I think it's silly to keep a record of it, or to even worry about it!!

Just set it, and go fly!!!
Were you born an *******, or do you just react to people that way?

(In my best DeNiro impersonation) You talking to me?? Are you talking to me??? Ain't nobody else here, so you must be talking to me!!!
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Old 06-08-2012, 06:44 PM
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Default RE: 25FX tuning problem?

The motor is mounted upright. It did not run good. I ran it more today and allowed it to rev alot more than the first break in runs. It runs very well now that I have the low end needle adjusted in far enough. I would have never considered flying the plane anytime before about the tenth adjustment. It was unreliablke andunacceptable for flight. Will It continue to run well, I don't know. It took 12 adjustments of 30 degrees each from as received to get there. I think that is strange. Other motors of the same brand have not given me an experience like this. The literature from the manufacturer leads me to believe that this would be unusual. I think there is something wrong and it probably has something to do with the low end needle valve. I'm going to call the manufacturer and find out. I thank the people here who gave some useful advice and apologize for a crude remark. I was/am frustrated and felt alot of the comments given were very condescending. I'm sure I was wrong. Thanks again.
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Old 06-08-2012, 06:49 PM
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Default RE: 25FX tuning problem?

Dude....you are making this waaaaay to difficult!!!
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Old 06-08-2012, 07:58 PM
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Default RE: 25FX tuning problem?

Quote:
It took 12 adjustments of 30 degrees each from as received to get there. I think that is strange. Other motors of the same brand have not given me an experience like this. The literature from the manufacturer leads me to believe that this would be unusual. I think there is something wrong and it probably has something to do with the low end needle valve. I'm going to call the manufacturer and find out. I thank the people here who gave some useful advice and apologize for a crude remark. I was/am frustrated and felt alot of the comments given were very condescending. I'm sure I was wrong. Thanks again.
It's obvious you don't have children.
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Old 06-08-2012, 08:11 PM
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Default RE: 25FX tuning problem?

Can you imagine what would happen, if the sticky part of the diaper fell off, and he had to replace it???
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Old 06-08-2012, 11:06 PM
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Default RE: 25FX tuning problem?

Agreed the needle position is a bit weird, but seriously, if you can get the engine running right it really, really doesn't matter where the needles wind up.
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Old 06-09-2012, 06:25 AM
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Default RE: 25FX tuning problem?

Hi!
What matters though is your tank position! Glow plug, fuel used, prop size etc.
Have you mounted it according to "the tank mounting rule"?
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