Any hope? ST (Itlaian) ST .25 ? (ATTN: LONG)

Years ago (early-mid 80's), I was very involved in the rc air hobby -- mostly pattern and sport acro. I left the hobby for years, and have
returned with a vengence over the last few of years.
One of my favorite planes was the built-up Super Sportster (don't ask), and I had a particular fondness for the SS 20. That plane was powered by a ST .25, which had a very aggravating problem. It would invariable quit about 5 minutes into a flight. It didn't sound lean, rich, or seized, it just QUIT. You could run it on the test stand all day long, and you could also run it in the plane on the ground all day long -- in mixed attitudes and throttle combinations. I learned a great deal about spray bar positioning, low and high needle setting, and even managed to get past the ubiquitous mid-range stumble (or at least thought so). The 2 ST .61's I had, after their initial teething, were great engines. The .25 ALWAYS suffered the sudden inexplicible sudden stoppage about 5 minutes into flight, but ONLY during flight. Eventually, that stoppage killed the plane when it happened in a low-level maneauver over rocks. The engine was cleaned up, after-oiled and stored.
I was very recently given a SS .20 from an estate that had a used-up OS on it (no compression). Initial thoughts went to trying to find some way to use the ST .25 (other than as a boat anchor). Have any new thoughts about the older ST's come up while I've been away? I tried multiple different glow plugs, the carb settings, replacing the fuel, clunk, filter, and all tubing -- all to no avail. I've tried many different fuels, and while the ST .25 seems to prefer the 5% nitro, even at out high field altitude (>3000 feet). The one thing that I never remembered trying was going to a larger-than recommended prop diameter.
I susupect these answers have been dealt with years ago, and from the old comments I've found, it looks like ST's may be more suited to decorative uses than others. The engine has been torn down, with no signs of wear or corrosion, and there is no evidence of carb leakage. Fuel is pressurized using muff pressure. Compression is good. Starts easily. The glow plugs look okay. Not burned out, and the catalyst looks okay, with no obvious burning/flaking. Would a Perry carb be likely to solve the problem? If there was a good chance of it doing so, I would be willing to go that route. The ST .25 was a great match for the SS 20, at least when it was running.
Should I even attempt to resurrect this engine, or would I be best in pursuing another brand? Whilst on that subject, what do you think about the GMS engines? I have a couple of larger GMS's I'm pleased with, but nothing this small. Just for sake of principal, I'm inclined to spend more and order an Irvine (or GMS) from Just Engines, before payig less at Hobbico/Tower.
I have several other reliable .25's, but these are all on funtional combat ships, and I hate to start stripping them as combat is a nearly weekly thing here with a couple of local friends. On a few occassions we actually have some out-of-town guests and have a real "group".
Sorry for the long post. I have no local resources. For years, I was the only on in this region interested in RC, and even now, with the friends I've interested, our "club" numbers 4, and I'm the "old-hand" (scary, no?) The nearest real club is a bit over 100 miles away, and aren't particularly friendly to non-locals (even if you're a dues-paying out of town member, you're welcome to watch at their flights or meets, but they don't really want you flying, or even appear to be interested in mentoring). The "LHS" is the same way, a bit over 100 miles away, and not too knowledgeable at that. Basically carry Hobbico/Great Planes and that's it.
Bob
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I'd stick it in the plane and see how it runs. Er, I wouldn't do any low passes during the shake down runs, tho. ;^)
CR
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Well, just to make yourself happy, clean it up, put on a new glow plug, grab some fresh fuel, and go fly it. That's the only way you can make yourself feel that you gave it everything you could.
I've never tried to heal an ST, so I don't have any miracle advice. I did spend a few hours on an ASP .25 to no avail. I forget the symptoms now. I traded it in for $20 at RJL for a GMS .46, which gave me loads of fun for a couple of years until a friend broke the plane it was in. The net cost of the .46 was something like $60 plus shipping.
I think the RJL trade-in may still be available.
Two brands I have confidence in at the low end: Thunder Tiger and GMS.
My one Magnum didn't give me happines (.15 XLS). Others have had success with that same engine. Must be my fault.
And, of course, there is always OS. Except for the FX stinkers (all .46 size?), every other OS engine I've had or helped to run was a sweetheart. They cost more, but, as a general rule, they work right out of the box.

I had an Irvine .40 hand-me-down. Once I picked a piece of trash out of the needle-valve barrel, it worked great. I didn't like the plastic backplate. I over-tightened it, had a lean run, and ruined the backplate. My bad. Go and do otherwise!

I have a GMS .32 and a TT .36 on two Gremlins. They both have given long service. Both have been crashed. The carb for the TT is being held on with JB Weld. I think the TT may have more power--but that may be a biased judgment, influenced by the small difference in displacement and cost.
The sound of the GMS engines is generally more annoying than that of the TT or the OS engines (even with the baffles removed from the mufflers). It bothers me a bit, but the low cost of the engines helps take the edge off the irritation.
                Marty
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That did it! Now I have to run my GMS .32s and .47 just to hear the annoying noise. <G>
Ed Cregger
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in

Let me know how the 'speriment turns out.
If you don't like the sound, I'd be happy to buy both of them from you at a premium used-once price. :o)
            Marty
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Martin X. Moleski, SJ wrote:

sorry its a bit long but this is how to set up the carb and as recommended by the UK importer a few years ago
Super Tigre carburetor adjustment procedure
The Super Tigre carburetor has two needle valves for adjusting fuel mixture. The # 1 needle is the high speed adjustment needle (on left as viewed from rear of engine, the needle closest to the fuel inlet nipple) . The # 2 needle (on right as viewed from rear of engine, and close to the throttle linkage attachment) is for slow speed adjustment. Newer Super Tigre carburetors have gone to a recessed screw in the barrel for slow speed adjustment. The idle speed adjustment screw is located to the left of the carburetor throat (as viewed from rear of engine). The screw on the right of the carburetor throat (as viewed from rear of engine) is the barrel retaining screw. Super Tigre carburetors have been maligned by some modelers as being hard to adjust and too finicky. My 30 plus years experience with Super Tigre engines has taught me to make any carb adjustments in very small increments, and once they are properly set they stay that way. If you are used to cranking a needle to turn to try and improve a condition, you will never get a Super Tigre carb adjusted properly. I have had properly adjusted Super Tigre carburetors go from too rich to too lean in less than a turn of the low speed needle.
To set up this carburetor you will need a short piece (1 foot) of clean fuel tubing.
First the idle speed adjustment screw needs to be adjusted so that the throttle barrel is open about the diameter of a modeling T pin. Later after the idle and mixture has stabilized and the engine is mounted in the aircraft this setting can be backed off so that the throttle barrel will close all the way with low throttle and low throttle trim to kill the engine.
Open the throttle barrel wide open, then with the length of clean fuel tubing attached to the fuel inlet nipple, blow through the tubing. Screw the high speed needle in until you hear no air escaping. Now open the high speed needle 2-1/2 turns.
Now with the throttle barrel at the previously established closed position, gently blow through the tubing. Adjust the low speed needle in until you can barely hear air escaping. Now open the low speed needle turn from this position.
Bear in mind if your change the position of the throttle stop you will have to reset the low speed needle. Also the setting on the high speed needle will affect the low speed transition. I have had the best luck trying to get a reliable idle and good transition with brand new Super Tigre engines after they are properly broken in. I have run as much a two gallons of fuel through Super Tigre ringed engines before the idle and transition stabilized to an acceptable level. The breaking in of a Super Tigre engine is time consuming and if not rushed, will reward you with an engine that should almost last a lifetime.
With the engine mounted on your aircraft it is time to start it. Fill the fuel tank and open the carburetor wide open. With your finger over the carburetor throat (and glow plug driver NOT CONNECTED) Bring the prop up on the compression stroke and slowly turn it through one revolution. You should see fuel flow into the fuel line and into the carburetor, flip through about two more revolutions with your finger over the throat. If when you remove your finger from the carburetor throat and the fuel in the fuel line flows back into the tank, this could be an indication that your fuel tank is too low relative to the carburetors center line. Go to low throttle, high throttle trim on your radio. Connect the glow driver and with a ckicken stick flip the prop through until the engine starts. Some of the hotter Super Tigre engines that I have had had a propensity to start in reverse. If this is the case try rotating the prop backwards against compression and letting it pop back. Usually the engine will start and run in the proper direction. If the engine starts and will idle fairly well, let it run for a minute or two to allow the engine to come up to operating temperature. Advance the throttle slowly to wide open. Listen to the engine and determine if its four stroking or two stroking. If its four stroking screw in the high speed needle until the engine transitions to two stroke. Now open the high speed needle until the engine just goes into four stroke. Back off the throttle to idle and have a helper hold the aircraft. With the helper holding the aircraft advance the throttle to wide open. Have your helper point the nose of the aircraft to the sky. If the engine speeds up to a stable two stroke, the high speed needle is set properly. If the engine is new, I generally open the high speed needle about 1/8th turn additional to ensure a rich high end until its broken in.
Once the high speed needle is set, return the aircraft to the level position and set the throttle to low throttle/high trim. If the engine is idling let it idle a few seconds then slowly advance the throttle. If the engine burbles, and it may spit fuel out the throat, its too rich. If this is the case, close (clockwise) the low speed needle about 1/8th turn. Run the engine to full throttle to clear it out then return to idle for 10 to 20 seconds then slowly advance the throttle. Repeat the above procedure until you have a smooth throttle transition. If the engine sags and hesitates with no burbling it means the low speed needle is too lean. Open (counter clockwise ) the low speed needle about 1/8th turn and try it again. This is the most time consuming part of adjusting any model engine carburetor so be patient. Once you are satisfied with the idle and transition return the throttle to wide open and recheck the high speed setting as per the previously outlined method and make the necessary small changes, then fly.
Note: Do not be tempted to short cut the break-in, burn at least a gallon of fuel with the high speed set rich. After break-in is accomplished do not try to adjust to the last few higher rpms, as this is the quickest way to turn your Super Tigre engine into a so-so performer (or worse) rather than a star performer. Also do not use the glow plug that came with the engine, substitute an OS #8 plug.
Some have reported that the venturi can be rotated from its straight down position to a slightly forward facing position to improve low speed transition. I have never encountered a problem that made this necessary, but it remains something to consider if all else does not give satisfactory results.
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wrote:

I appreciate the time you spent in answering my post (and yes, I still have the manual). However, unfortunately, BTDT. I actually burned a bit over a gallon of fuel on the test stand before even putting the ST in the plane. You are correct in your statement that the ST needles, especially the low-speed needle can be finicky. Once broken-in and tuned, the engine ran like a champ on the stand. Also, ran like a champ in the plane, at least on the ground. No evidence of overheating, so far as I could tell. No loading with prolonged idle, good transition, and excellent higher throttle response, and no ebvious evidence of leaning out in flight. My early thoughts were leaning out when the engine unloaded, but even running it rich didn't fix the problem. The problem would occur anywhere from 5 to 7 minutes into the flight, with the engine suddenly quitting. No sputtering first, as though it was going rich or lean, and not the very sudden stoppage I associate with an engine that is seizing. Breakdown of the engine never revealed any noticeable wear or scoring. Although I fiddled with the positioning of the spray bar, I really wasn't able to notice a difference unless I really got it way our of it's correct location. I tried many different glow plugs (and fuels), and settled on an OS#8 as it seemed to work best. This was all back in about 1985. After the plane was killed during a low-level engine stoppage with nowhere to deadstick it (bunch of big rocks), I tore down the engine, which still looked fine, oiled it up for storage, and it sat there until a few months ago. By now the engine has had probably 4 - 5 gallons of fuel through it. Tore it down and inspected it, reassembled it and re-tuned it, and it's back to its old tricks just as before (but did the air-testing on a SPAD this time). And yes, it got new gaskets, etc. I simply don't understand it. Runs GREAT on the stand, in any position, ditto in the plane whilst being held in any position, but about 5-7 minutes in the air it simply abruptly quits -- almost as though the fuel is being shut off very close to the fuel inlet. I've changed tanks, clunks, tubing and filters to no avail. About the only thing I haven't done is change the carb or put a pump on it - but would just replace the engine prior to doing that. I think my next step will be just to replace the engine, perhaps taking advantage of one of the trade-in programs. A bit of a shame, because when it's running, it runs very well, but I'm not willing to limit all my flights with it to 4 minutes.
Bob
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Your description of it running fine on the ground but having problems in the air is the typical description of a model suffering fuel foaming from vibration.
As soon as the landing gear is lifted from the ground, the models tendency to vibrate at a given frequency changes, throwing off the needle settings beyond a human's ability to adjust in anticipation.
Isolating the fuel tank from vibration, or, in a worst case scenario, spritzing a couple shots of Armor All into your fuel and shaking well, will often cure this malady.
The Super Tigre engines had nothing wrong with them to cause such a problem. I think real world physics are giving you a hard time this time.
Ed Cregger
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Excellent, Ed. I think you hit it on the head.
Time to more carefully balance the prop, and check to see that the tank is well padded with closed cell foam, not the other kind like that is found in chairs, and that there is not a long length of fuel line that is unsupported and vibrating like a string.
--
Jim in NC


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On Sat, 14 Oct 2006 22:01:00 -0400, "Ed Cregger"

That's an excellent thought, Ed. The tank was well encased with closed-cell foam. If anything it may have been wrapped too tightly. The lines were kept as short as possible, with no unsupported segments or loops that could flop around, both on the tank outlet (carb side) as well as as much as possible on the inlet (muff) side. At one point, I had been using a quick-fill valve, but removed that thinking that it may have been leaking either allowing pressure loss or bubbling, but that was removed long ago. I did use a sintered clunk, thinking that it might filter bubbles or foam out ahead of the true filter, rather than a standard clunk, but that obviously didn't help. However, I never thought to try a defoamer such as armor-all. I'll give that a shot, and I'll revisit the tank wrapping as well. It may be that I have the tank wrapped tightly enough for vibration to be transmitted in that manner (it's a very snug fit in it's present location). I never noticed foaming in the fuel line after a dead stick, but I don't really remember looking for it, either.
Your idea just makes more sense than anything else that I've been able to come up with, particularly when you consider the engine normally works so well up until the point that it quits, and that it only quits during flight. Even more indicting (in retrospect) is the fact that regardless of the flight time prior to the stoppage, the tank was usually about 2/3 full after the dead-stick (based on what was removed from the tank at the end of the flight).
Thanks for the ideas, and you can be sure I'll investigate this and let you know if it fixes things. I'm going to feel really stupid if this turns out to be the source of the problem. I do find it a bit strange that the same thing is presently happening during testing on a SPAD, where the foam wrap as well as the mounting is quite different. I'm using cool-power fuel, and don't have a foaming problem with any of my other ships, at least not so far as I know -- and certainly not to the degree to cause this problem.
Bob
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The hideously evil thing about foaming is that it is gone a fraction of a second after the engine quits. You never will see it. It is like faith; you just have to know it is there! <g>
--
Jim in NC


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On Sun, 15 Oct 2006 02:43:47 -0400, "Morgans"

Pretty much what I figured, but I had thought that there might be some residual bubbles in the high point in the carb line.
Question:
Due to the location and size of the tank I was using in the SS, I was using "foam rubber" (the same stuff used wrapping most receivers) around the tank. Due to the size of the opening in the former, I had to tightly wrap the foam around the tank, and then fairly tightly wrap the whole mess with 2" wide clear packing tape so that it would fit in the former. Would this have likely contributed? My normal useage is to gently wrap the tank, often bypassing the tape, and allow the formers to hold the foam around the tank (and within the former cavity).
Currently, during the present testing mode, I'm using a SPAD profile design, and the tank is rather gently wrapped with the same type foam, and is then held in place with a couple of plastic zip ties, and I am having the same problem, although I may be getting closer to half a tank prior to the sudden cessation of engine activity (same tank size as before, but new tank and fittings). I can accept trashing the engine and moving on, but it's now become a matter of principal (or stubbornness).
Whatever I do, I don't want a known problem engine to be the demise of the "new" SS that I was given from my old friend's estate (esp. as SS's are only available as ARF's or plan/scratch builds now). It's a fairly nice plane that he and I flew together a good bit, and he would want me flying it, and not using it as a hangar queen. I've been at this long enough that I rarely lose a plane to pilot error (but when I do, they're spectacular crashes). I'd just hate to lose this one through stupidity. He and I went back a long ways, and he treated me as a father in many ways, so there's a lot of sentiment involved. Probably why I'm prattling on so much about as inane a subject.
Realistically, I'll probably either rebuild his old OS if I can get parts for it, or shoehorn a GMS 32 into it; but I'm still going to try to figure out this ST. It's a great little engine when it's working, it just needs too many work breaks (sorta' like my employees).
Bob
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wrote:

Along the lines about foaming fuel: A few of us have been flying Accel Profile Katanas(too many of us!) and the tank is mounted on the side with zip-ties(ty-wraps?) Some did have a foaming problem from the zip-ties being too tight that was not apparent on the ground . I guess it makes sense that 3 points of the plane touching the Big Ball would dampen the vibration as opposed to being in the air. Anyway, better rubber aroound the tank and not-so-tight zip ties fixed that problem. mk
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Ed mentioned the ol' Armor All trick too. That has to be seen to be believed, if you haven't tried it.
Take a fresh gallon of fuel and shake it. Observe the foam formed (even in the fuel that claims to have "anti-foaming" additives). Add two drops of Armor All. Shake again. Foam? Add another drop. Repeat as necessary. After a very small number of drops, foaming will just completely stop happening! It really works, and seems to have no ill effects. If you have the slightest hunch that foaming might be a problem in one of your models, try the Armor All treatment on your fuel and you'll eliminate foaming.
Good flying, desmobob
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I've been following your thread but your last account gave me a shiver. The RC gods must not be happy. I suggest a sacrifice. :) mk
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wrote in

OH, my!
It's been years since anyone in the group called for a sacrifice!
In the old days, I think it had to be an Ugly Stik.
Dunno what the exchange rate is these days.
            Marty
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Martin X. Moleski, SJ wrote:

Whaaaaat!?!?!? You're a Jesuit AND a college perfesser and you don't know? Oh, dear!!! ;-) Does this have anything to do with ST's no longer being Italian-made? Talk about blasphemy!!! Oy, vey!!!
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Pasta faggiole!
            Marty
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wrote:

Hoo boy, looks like I've stepped into it now.
Being a simple hick from the boonies, with no club, only a couple of nelatively new RC'ers (that I more or less shanghaied so as to not always be flying alone), and definitely no nearby place of organized RC worship, I am in sore need of instruction from those of you here.
I realize that there is an entire pantheon of RC gods, rather than a single true RC god. I have had more than a passing familiarity with a few over the years. Such as the god "dammit" that controls the untimely placement of the feet of backwards-walking spectators -- seems to have a preference for wings over empennages. The god "oh-shit" that seems to have control of most things concerned with controlled powered flight, and the departure therefrom at the most inopportune moment. Of course there's the lesser god "oops". that appears to be the henchman of "of shit", but with generally less drastic outcomes for both the modeler and the model. Mustn't forget the god "uh-oh" that reigns supreme over the realm of radio-frequency communications. Yes, the one that ensures that a "charged" pack dies during your flight, mysteriously causes you to switch your computer radio to a different model during your flight, or blocks your signal entirely just because you flew near some wires that you believed only carried telephone service. He's the one that delights in YOUR acrobatics with the transmitter whilst your model flies whither it will, almost certainly coming to a bad end. He's also the one that makes certain your fail-safe settings will fail if they are needed and supposedly available. There's "not again" that seems to control most things encountered with IC engines, whether it has to do with mysteriously changing needle settings, or grabbing hot heads. He is also the patron saint of plastic surgeons, for those modelers that seem to be unable to keep their fingers out of the prop arc of a running engine. Then there are at least a couple of gods whose names I quake to even mention here that control the building process -- yes, "%&*@##" and his friends that assure that you build 2 left wing halves, or build the wing right-side up over the plans, when it was supposed to be the other way, or omit doing something in an area that becomes inaccessible later during the building process.
I feel certain that the pantheon is much larger, but without access to formal RC worship, these are the only gods that I recall becoming acquainted with over the years. If someone could help me to fill out the roster of gods, it would be much appreciated.
Now, as to intentional sacrifice. As has been already stated, I'm certain that the time is nigh for a sacrifice to be made to resurrect this baby ST engine. The fact that it is Italian and not Chinese will no doubt increase the conversion factor, but I am sorely lacking in understanding the conversion factor in the first place. Can appropriate recommendations be made? Must the sacrifice be planned in advance, or will the next sacrifice to come along be adequate? Must the sacrifice be virgin, or will one whose weight in epoxy equals or exceeds the weight of balsa be adequate?
Further, will the sacrifice need to be made to a specific god or group of gods, or will it require a convocation of the entire pantheon -- and how does one make certain the correct gods are in attendance in the first place?
(Sorry guys, this is what happens on a very rainy Sunday afternoon, when it's too nasty to even run a boat, if I were into boats).
Bob
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"Everybody" has to go on the list, as in:
"Hey, Everybody, watch this!"

Not that I've attended the pagan rituals, you understand, but I seem to misremember that they called for an Ugly Stik to plunge headlong into the center of the field. How such things were arranged was known only to the initiates of the cult, of course.

If you have to ask, the initiates can't tell you. :o(

I'm enjoying a 5-day weekend in Buffalo, thanks to our first snowfall of the season. Last weekend, we were out in T-shirts at the field.
                Marty The Big-8 hierarchies (comp, humanities, misc, news, rec, sci, soc, talk) are under new management. See http://www.big-8.org for details.
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