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os .25 FX questions

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Old 07-11-2003, 01:21 AM
  #1  
mattijs
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Default os .25 FX questions

I recently bought a .25 os Fx. After i burned it in with about 12 oz total of very rich running i went flying with it and have so the last couple of days. While i do appreciate the ease with witch it starts, it seems to me that i can't get it running supersmooth....I had one deadstick in 13 flights or so but what struck me was the trouble it took for the engine to rev up when it had been flying on idle for a while....Is that normal???? Only when i leaned it out enough (the flight it went deadstick) it seemed responsive like it is on the ground.


The prop is a 8-8 graupner because the rotor-ground clearance isn't enough for a 9-5 or 6

Tank is placed right behind the firewall with all new tubing (except for the fuel filter)

standard muffler

Is it the prop?
Is it not "burned in enough"?
Has it got something to do with the low rpm needle on the carb. (i don't know what to do with it)
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Old 07-11-2003, 01:32 AM
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DBCherry
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Default os .25 FX questions

Well, aren't the FX series ABC engines? If so, they should NOT be broken in rich. You can destroy their compression.

Don't know if it would affect it in the way you're describing though. Problems with transition from idle to full throttle is usually the low end needle. You might try leaning the low end a bit.
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Old 07-12-2003, 03:30 PM
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Default os .25 FX questions

WOW first time i hear that....How would I be able to tell wether or not the 'compression' is already broken....The sound of the engine when full throttle is fairly high pitched so i geuss it still is getting the correct rpm for a 8-8 prop (i have no tachometer)

What does ABC stand for and why can't you burn them in rich???
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Old 07-12-2003, 03:35 PM
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Default os .25 FX questions

also, 1/2 of the times i start it (with a set of pliers, i just started handstarting because my battery was empty....the pleirs have a soft handgrip with wich i rotate the propeller)....It starts runniing in the wrong direction, I thought only older engines with a different cranckshaft could/would do that????
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Old 07-13-2003, 03:26 AM
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Default os .25 FX questions

ABC stands for: Aluminum Piston runing in a chrome plated bronze sleeve. In the case of O.S. they use a nickle plated bronze sleeve.

Yes an ABC or ABN type needs to be broke in hard. Doing a brake in very rich can damage the piston sleeve to the point that the engine will never perform up to specs.

Here is why: The bronze sleeve expands at a faster rate than the piston with heat so to obtain that perfect piston clearance at operating temperature when cold the fit is 'squeaky tight' at the top of the cylinder (the sleeves are taper bored). When starting it is neccessary for the sleeves to expand quickly so the proper clearance fit is acheived. A blubberery rich run will not allow for this expansion and the piston/sleeve can be damaged.

As far as your throttling problems go it sounds as though your low range needle is to rich did you ever adjust it per instructions?

John
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Old 07-13-2003, 11:23 AM
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Any glow engine can start and run (poorly) in reverse. They will quit when throttle is advanced.

John gave you the straight dope on ABC (& ABN) engines. Too rich causes excessive wear to the sleeve.

For what it's worth, that 8 X 8 prop might be a bit much pitch for the engine. I'm sure others will jump in here, but I'd think 9 X 5 would be more like it. (I've been wrong once in a while though.)
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Old 07-13-2003, 04:26 PM
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I use an APC 8x6 on my 25fx .The motor runs like a top.
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Old 07-13-2003, 06:57 PM
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The .25 FX is a fairly powerfull little engine in its class. One properly broken in will turn an APC C-2 9/5 in the neiborhood of 14,500 RPM and spin a C-2 9-6 around 14.000 on 15% fuel. The special pylon props that Fred Burgdorf of APC moulded for .25 pylon racing are 9.25x5.5 narrow blade and 9.25x6N and they are about optimum for most good sport .25's. If you use the eight inch diameter you will get a bunch of noisey RPM but pay for the noise in reduced Overall performance.

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Old 07-13-2003, 08:45 PM
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bulletbob
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I have the .25 and .46Fx engines. Both owners manuals say to break in the engines in a rich, full throttle situation and not to run them in hard. When all else fails read the directions.
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Old 07-13-2003, 09:05 PM
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And many have commented that OS includes break-in procedures from their old non-ABC engines.

I stand by my assertion. Do NOT break in an ABC engine by running it rich.
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Old 07-13-2003, 09:13 PM
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Bob What the manual means is to break it in a rich backed off from peak in a two stoke condition not in a blubery rich four cycle condition and to do it at full throttle. Never break in any ABC, ABN in a blubbery rich condition or you will end up with second rate or worse engine. Those initial thermal cycles are absolutely critical to the life of an ABC/ABN engine Run it at the proper temperature or ruin it.

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Old 07-14-2003, 01:03 AM
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mattijs
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Default os .25 FX questions

if only I had a tachometer.....You guys got me really woried. Does a degraded ABC still start at the first flick??? Mine does....And what is blubbery rich??? There was alot of residu on the fuselage after the first 4 oz.tank run, but i don't think the needle valve was turned open more than 2 maybe 2.5 turns....
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Old 07-14-2003, 01:39 AM
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mattijs,
If you haven't run the engine all that much, don't worry about it. Chances are that you haven't done any real damage yet.

Okay, "blubbery" rich. I used the term so....

When a 2 stroke/cycle engine is tuned fairly lean, it runs in a 2 cycle mode. In other words, it produces power every stroke. So at full throttle it will have a rather high pitched "whine". (The engine will seem to be running smooth.)

Whereas, if it's "4 cycling" (or quite rich) it's only producing power, or firing, every other stroke, and the sound it produces will be more of an intermittent "bra-a-ap". In a four cycle run it will also sound "wet", if that makes more sense. (And will produce much more smoke and residual oil out the exhaust.)

A tach isn't really necessary. I'm sure you've already heard the sounds, you just don't trust what you already know.

Once you do understand what 2 cycling, or a leaner run, sounds like, try a "pinch" test. Pinch test = with engine tuned to a 2 cycle run, at full throttle, pinch the fuel line going to the carb (and hold it). If the engine is tuned properly, you will hear a slight increase in RPM's (an increase in the pitch, or a slightly higher "whine"), then it will quit. If the engine just quits, it's set too lean, and you need to back out the needle a few clicks (3 or 4) and try it again.

Good luck,
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Old 07-14-2003, 01:58 AM
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Default os .25 FX questions

mattijs My apologies for using a local slang term. When starting that engine (I prefer to do the start further open on the needle about four turns) after starting it will be very rich. then just turn the needle in untill the engine will accept full throttle and stay running, leave the throttle full open. At this point it will still be very rich and running unevenly This is what sometimes is called four stroking and I called Blubbery rich. This is the setting you do not want to run for long at. Now continue to screw the needle in and at some point there will be a sudden dramatic rise in RPM (you don,t need a tach) and it is after this sudden rise where you want to operate the engine for those initial runs, It is now said to be running in a two stroke. After there have been a few tanks through it then you can go ahead and run to peak rpm by turning the needle in more untill the engine will turn no faster, This is peak now just back off the needle untill it drops around five hundred RPM and if you do not have a tack just back off untill there is a noticible drop in speed. This is a good flight setting, if the engine will hold this setting then it is broke in enough to fly.

At the needle openings you described I think you are ok (it is a great little engine). And needle setting becomes intuitive after a while.

When it is running well at high throttle then it is time to set the mid range needle This is a small slot head screw in the middle of the throttle arm. Pull the throttle back to a reasonably slow idle and let run slowly for a moment and advance the throttle, If the engine stumbles and accelerates slowly then it is to rich. screw that slotted screw in clockwise a very tiny bit perhaps a 1/8th turn and try agine. If the engine dies immediately when you open the throttle then it is to lean, just turn that screw counter clockwise a tiny bit and try agine. You will find that sweet spot.

You will be OK, Enjoy

John
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Old 07-28-2003, 10:21 AM
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Default os .25 FX questions

Hello,

I have some questions and remarks on this topic that may be of interest.
I got an 25FX and a 46FX from OS, and I want to share my experiances with those engines.
First the 25FX, it was broken in rather on the rich side and I'm flying it for a long time with a 9x6 prop with works very well. This engine is running on a mixture 80-20, and the oil is castor-oil (no nitro). I had no problems so far, it's still running well after 3 years (although i ran it in "blubbery".
But the 46FX is a different story. Running in "blubbery", fuel 20% castor oil, 5 % nitro and a prop 11x7. That engine was running perfectly for 100 flights before troubles started. The ballbearings were no longer good. When opening the engine, I found some small metal parts in it which caused the failure of the ball bearings. This metal was the nickle from the sleeve that was coming off ! Whitin 50 more flights, engine was ruined because this nickle was peeling off.
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Old 07-28-2003, 10:33 AM
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continued...
The same happened to an another member also with a 46FX. So he bought a new FX and I did the same. This time both running on a mixture of 10% castor oil and 8% synthetic oil (Titan oil). This time both engines ran longer but after a year same thing , the nickle came off. There are other 46FX at our airfield running on synthetic oil only and they do not have any problems.
What I think that happened (only my opinion, nothing more)
on castor oil you get black "soot" in the engine (I don't know the exact word but I guess you all know what I mean). This cause the temperature to rise and than the nickle is coming off.
This was the case to a total of 7 engines I know (also at other airfields they had the same problems)
If someone has some similar experience, please let me know.

With the 25FX nobody has problems as far as I know, maybe this is still a true ABC and not a ABN.
My conclusion is not to run a 46FX on castor oil !

I would like to know if I'm right on this topic

kr,
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Old 07-29-2003, 08:07 PM
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Several years ago, this was a problem with O.S. engines in the States (Only the .46 fx that I'm aware of). It did not have anything to do with the castor content that I recall, just a thin layer of brass. Although it seemed like it was common due to the internet, I believe the percentage was under 1% of all engines sold.

O.S. made good on their warranty claims, and as far as I know, they have fixed the problem. Maybe Europe still has some of these older engines in stock. I have not heard recently of a New O.S. with this problem.

BTW, I own about 10 OS engines, probably half of them are the .46 fx. I've had no problems with them to date, running Omega 15% fuel which is a combo of Castor and Synthetic oils.
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