New OS .25FX Question ..........

Tell us what you do to get the best performance from your engines.

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Fred420
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New OS .25FX Question ..........

Post by Fred420 »

I just got a new OS .25 and started it up today for the first time. It has been raining and with my schedule as an Umpire and my other job ..... this is the first time I could try it, static in the garage. Love the noise as it fired up and the smell of Nitro [^]

1st tank .... 15% Wildcat, supplied plug and a APC 10-4 prop, it started right up. Ran a tank thru it, real rich, then, lean for awhile. Did this back and forth for about 1 min each setting and ran a tank full.

2nd tank, did the same procedure, then peaked it out and checked RPM's. Peaked at 12,200.

I am going to run 2 more tanks, this time with 30% Wildcat Heli and a MAS 10-4 prop to see if there is a differance.

Hope this can peak around 14,500. Any thoughts??

I am going to Bryan, Ohio Sunday so that will be the first time in the air for it ........ and my first meet of the year.
Hat Trick
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Post by Hat Trick »

You need a 10x3 APC or a MA 10 x 4 . You'll never get to the limit with a APC 10 x 4!

Some recommend breaking in with a smaller prop to let the RPM turn up a lot more and to use high nitro fuel for the break in. You want it turning fast but running very rich and well lubricated!
RH
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Post by RH »

Dave, I wish you would have asked while your new FX was still in the box.....here is the breakin proceedure I follow for combat motors

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">For an ABC engine you want to get it running and get it hot as soon as possible, then let it cool off. To do this, we run a slightly smaller prop, get the engine running, lean it out and then back it off just a tad, you don't want it dead lean. Let it go for 2 minutes, then shut it off and let it cool overnight. Do it again tomorrow, let it cool completely. Now, your engine has made it through the largest thermal changes that it will in it's lifetime. You may now fill the tank, put on the prop you want to use and run the engine 1/4 turn richer than lean and let the enigne polish itself. If this is enough power to fly your airplane (and if it isn't, you need more engine anyway) put it on the plane if you can get the engine to idle satisfactory. A good way to really polish on the engine is to fly loops with the plane, going up the engine will lean out and get a little warmer, then going down it will be richer and cool off. Couple flights of that and your engine will probably be 95% finished and will only improve with a bunch more flying. You should be able to set a really nice low idle.

If you break the engine in rich, it won't get up to temp, it will grind the top of the piston away and you will have a pretty good sport engine. Done correctly though and you will have an engine that performs a tad better than the other guys.

George Aldrich used to say, 'Buy the engine that squeaks the loudest when you turn it over at the shop, you can't buy one that is too tight.' Keep it that way.
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sgilkey
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Post by sgilkey »

Dave, just about any bone-stock FX will get 14-14.5k or even better on the 10x3APC or 10x4MA prop, using 15% fuel. The 10x4APC will be more load so that is one problem for you. A MA 9x4 or even a 9x4 cut down to 8x4 would be a better break-in prop, even for Limited B use. You want the engine running some pretty good revs, not lugged down on it's first few runs.

The other thing is the muffler. You need to remove the baffle, on the FX it's much simpler than on the LA where the baffle disk is part of the center section of the muffler. On the FX, the baffle is a separate piece that is between the front and rear halves of the muff. All you need to do is remove it, no other changes need to be made, the muffler just screws back together. While you have the muffler apart, make sure there is not a lot of casting flash around the junction of the header section to the can section on the inside of the front half, and around the stinger opening on the back half. Sometimes flash or manufacturing debris will partially block those openings. Finally, when reassembling the muffler, you want to just snug the thru bolt, then be sure to tighten the rear jam nut. If you really tighten the thru-bolt to a high torque, it has a greater chance of breaking when the muffler gets hot. Don't try to run the muff without the jam nut, it will eventually come apart. If you lose your jam nut I have some spares of the proper size and can give you one at Hillside. Good luck!
Rabbit Leader
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Post by Rabbit Leader »

I can agree with everything that's been said here with the exception of the baffle removal...never have needed to do that, mine tach up just fine. The FX is just a great, all round combat engine..
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Ed Kettler
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Post by Ed Kettler »

As long as you break it in properly, a stock 25FX will run 14.5 all day on 15% Power Master. About as bullet proof (or even container proof) as an engine can be built.
Steve108
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Post by Steve108 »

So I started breaking in my new 25fx today. It started up great, three or four flips by hand. Got it running full throttle, leaned it, and backed off about two clicks. About one minute into the run, the muffler loosened up. I tried to shut it down but it just went to idle. Put my finger over the carb, still running, set it really rich and popped the throttle open to kill it.

My question is, did I ruin this engine or should I just do the same thing tommorrow? After checking the muffler bolts of course![:I]
Alex Treneff
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Post by Alex Treneff »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Steve108</i>
<br />So I started breaking in my new 25fx today. It started up great, three or four flips by hand. Got it running full throttle, leaned it, and backed off about two clicks. About one minute into the run, the muffler loosened up. I tried to shut it down but it just went to idle. Put my finger over the carb, still running, set it really rich and popped the throttle open to kill it.

My question is, did I ruin this engine or should I just do the same thing tommorrow? After checking the muffler bolts of course![:I]
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Steve, if the only problem is that the engine would not die, check that they carburetor is fully closing if not, adjust the angle of the arm on the throttle servo to give it enough throw.
Steve108
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Post by Steve108 »

I was more concerned about the lack of a muffler making it run lean and ruining the con rod bushings or something like that.

Thanks
EK
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Post by EK »

FX's are pretty forgiving and can take quite a bit of abuse. With it still running at idle it's very doubtful the motor went lean or was lean long enough to damage it. You put your finger over the intake so assume the engine wasn't smoking. I break my 25's in similar to the LA's but don't push them as hard.
sgilkey
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Post by sgilkey »

I really doubt you caused any problem and wouldn't worry about it, if you shut it down reasonably promptly it probably didn't go lean and if it did only briefly it's probably still OK, the FX are indeed very tough and tolerate a lot of abuse, though a proper break in is ideal when possible! If the rod were hurt, I think you'd know it, a brand new rod will probably sieze/gall if it is starved of oil, if it didn't you're probably fine.
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