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OS .25FP Any good???

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Old 08-11-2010, 05:36 PM
  #1
iflyg450
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Default OS .25FP Any good???

Yup I am new to this u-control stuff. I have been flying a sterling yak 9 with a Fox 35, I hate having to have a special fuel for it. Last weekend an older club member offered up a lightly used OS 25FP for a good price. Is this engine anygood? performace wise is it better than the Fox 35?
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Old 08-11-2010, 08:23 PM
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DaveSR71
 
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Default RE: OS .25FP Any good???

Does it have a blue head?
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Old 08-11-2010, 08:24 PM
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Default RE: OS .25FP Any good???

The OS 25 will equal and possibly exceed the power of the Fox 35. It's a good engine that'll run on R/C fuel.
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Old 08-11-2010, 08:28 PM
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Default RE: OS .25FP Any good???

When the FP series went out of production I went around buyinig up all of the FP motors I could find, till thiis day I still have the 15FP, 20FP, 25FP, 35FP and 40FP in my collectiion, some new in the box (they are not for sale). I have 7 OS-25FP's in my collectiion, four of them will be used on a profile scale B-29. They are a great engine, remember it has a plain bushing but runs great. It being run for Stunt it might requiire some timing changes but worth buyinig.
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Old 08-11-2010, 08:31 PM
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iflyg450
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Default RE: OS .25FP Any good???

nope it does not have a blue head, what does the blue head mean?
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Old 08-11-2010, 09:31 PM
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Default RE: OS .25FP Any good???


Quote:
ORIGINAL: iflyg450

nope it does not have a blue head, what does the blue head mean?

Not real sure other than some kind of blue head OS .25 on another fliers airplane.
Was a new unbroken in engine and hard to start and wanting to seize so did not get to observe much about how it ran.

Playing 25+years catch up in C/L from this end.


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Old 08-12-2010, 05:46 AM
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Default RE: OS .25FP Any good???

The blue head and the rest of the motor for that matter is an OS25LA the successor to the 25FP.
Just one word on fuel. While the 25 will run on R/C fuel it needs a higher oil content then many of the cheaper brands of fuel. It is a plain bushing engine and needs more lubrication then a ball bearing equivalent. Something around 20%oil is at least the minimum that I would use. I personally run Powermaster 10/22 in most of mine but Sig and some others are all good. Stay away from all synthetic fuel mixtures for C/L. Since you have no throttle control if you go lean in flight you will have to run the tank out in that condition. Lifespan of your engine can go down the drain immediately. Bottom line is use a fuel with some castor in it.
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Old 08-12-2010, 06:55 AM
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iflyg450
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Default RE: OS .25FP Any good???

I use a omega 15% in all my planes then add obout 3oz of castor to a new gallon. I think for $25 this engine sounds like a good buy. It should move my Yak9 pretty good.
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Old 08-12-2010, 07:31 AM
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Default RE: OS .25FP Any good???

Quote:
ORIGINAL: iflyg450

I use a omega 15% in all my planes then add obout 3oz of castor to a new gallon. I think for $25 this engine sounds like a good buy. It should move my Yak9 pretty good.
That`s what I`m using as Omega is all I can get where I live, it only has 16% oil so it has to be spiked with 8 oz. of castor for 20% total for modern abc engines and 14 oz. for 25% total for older style steel piston plain bearing engines 3 oz. is not enough, I`d add at least 10 oz. You have a great little engine that has the same power as a Fox .35 and will run much better on a profile.
Good Luck
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Old 08-12-2010, 07:49 AM
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Default RE: OS .25FP Any good???

Is the FP a Steal Piston engine?
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Old 08-12-2010, 07:52 AM
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Default RE: OS .25FP Any good???

It's an aluminum piston in a nickle plated liner. They call it ABN construction.
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Old 08-12-2010, 08:18 AM
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Default RE: OS .25FP Any good???

Actually the FP was made in both ABN and iron/steel versions - at least the .20 and .25 were. I'm not sure any of the other versions.
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Old 08-12-2010, 04:27 PM
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Default RE: OS .25FP Any good???


Quote:
ORIGINAL: iflyg450

Is the FP a Steal Piston engine?
I don't know about the 25 but I can see the cylinder sleeve on my FP 40 by looking in the exhaust opening, if the sleeve is silver in color it's steel if gold in color it's ABN
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Old 08-13-2010, 05:59 PM
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Default RE: OS .25FP Any good???

I know the .35 was available in iron/steel P/L as well as ABC. AFAIK, the FP ABC's were actual chrome, not nickle.
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Old 08-13-2010, 11:35 PM
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Default RE: OS .25FP Any good???


Quote:
ORIGINAL: cutaway

I know the .35 was available in iron/steel P/L as well as ABC. AFAIK, the FP ABC's were actual chrome, not nickle.

No FP was ever an abc in spite of what might be on the box or the adds. They were origionally iron/steel then aluminum/ steel liner with nickel plating. OS only chromes it's high performance engines anymore, and they probably farm that out.
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Old 08-14-2010, 12:45 PM
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iflyg450
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Default RE: OS .25FP Any good???

A magnet sticks to the piston so I guess its a steel one, does this mean that this engine needs the same type of fuel as a Fox 35??
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Old 08-14-2010, 02:27 PM
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Default RE: OS .25FP Any good???

Ifly,

Same "type" of fuel, yes, but not 29% oil, all of which is castor.

OS instructions for the FP series, dating from about 1991, state that fuel containing 20% castor oil is "correct." No mention of any synthetic oil %... (Further details: OS recommended 75% methanol, 20% castor oil, 5% nitro for initial break-in and/or general use, AND, later, after break-in, up to 65% methanol, 20% castor oil and 15% nitro for higher performance.)

With an iron piston and steel sleeve, you shouldn't need any more than the recommended 20% total oil. Even with 20% all-castor, that's a lot less mess than 29% castor.

Since OS recommends all-castor, you may find that ANY synthetic % - say an 18% castor, 2% synthetic oil portion - could prevent the castor varnish build-up that older types of iron-in-steel engines found to be a good thing. As wear occurred, that varnish layer seemed to maintain good seal and durable life. Synthetics are detergent, and can "wash off" the layer as it tried to form. However, the detergent effect may not harm things if the synthetic % is up to 5% (i.e., 15% castor, 5% synthetic.)

Newer (ABC/AAC/ABN) engines are manufactured to expand to "ideal" tolerances at running temps. A varnish coating would change the heating and cooling, and disrupt that intended fit at operating conditions.


Dennis is right that no FP was ABC, but I think the later ones were ABN - high silicon aluminum piston in a nickle-plated brass sleeve. Tower Hobbies had a near clone of the 40FP (many parts interchange) manufactured for a while. One main difference was that the Tower 40 was true ABC (hi-silicon Al piston running in a chromed brass sleeve. )
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Old 08-14-2010, 02:43 PM
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Default RE: OS .25FP Any good???

Quote:
ORIGINAL: dennis


Quote:
ORIGINAL: cutaway

I know the .35 was available in iron/steel P/L as well as ABC. AFAIK, the FP ABC's were actual chrome, not nickle.

No FP was ever an abc in spite of what might be on the box or the adds. They were origionally iron/steel then aluminum/ steel liner with nickel plating. OS only chromes it's high performance engines anymore, and they probably farm that out.
I believe you meant Aluminum/Brass rather than aluminum/ steel.
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Old 08-14-2010, 04:00 PM
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Default RE: OS .25FP Any good???

Quote:
ORIGINAL: iflyg450

A magnet sticks to the piston so I guess its a steel one, does this mean that this engine needs the same type of fuel as a Fox 35??
Maybe not but I would add 10 oz. of castor to a gallon of Omega this will give you 22% total oil.
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Old 08-14-2010, 07:35 PM
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Default RE: OS .25FP Any good???

Well I think I just go with a OS 25LA-s I have been very happy with the way my Nobler flies with the 46LA-s it just runs so nice. I want to thank everyone who took the time to post some of the most informed information that I have seen on this site in a very long time.
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Old 08-14-2010, 08:08 PM
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Default RE: OS .25FP Any good???

Your correct it is aluminum/brass. Old age is catching up to me.
As has been said many times the OS40FP, the Thunder Tigre 40GP and the Tower 40 were all completely interchangable in parts. I have seen motors with parts from all 3 of the motors combined. But for my money the best was the Tower, 2nd the Thunder Tigre and a distant 3rd the OS fP.
If you see a Tower for sale on these forums or Flea bay and it looks good give yourself a treat and buy it
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Old 08-15-2010, 05:44 PM
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Default RE: OS .25FP Any good???


Quote:
ORIGINAL: dennis
...As has been said many times the OS40FP, the Thunder Tigre 40GP and the Tower 40 were all completely interchangable in parts. I have seen motors with parts from all 3 of the motors combined...
Not sure about the .40 but the TT .10, .15, and .25 all have sprinkler venturies with the needle valve to the rear instead of centered.
Here is a TT .10 venturi:

George
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Old 08-15-2010, 07:35 PM
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Default RE: OS .25FP Any good???


Quote:
ORIGINAL: iflyg450

Well I think I just go with a OS 25LA-s I have been very happy with the way my Nobler flies with the 46LA-s it just runs so nice. I want to thank everyone who took the time to post some of the most informed information that I have seen on this site in a very long time.
You still should not run Omega/CoolPower without adding oil to it Believe it ... you will have erratic, grouchy engines. If you use the 'Helicopter' fuel, you will have adequate oil content, but I don't believe it's available except as 30% nitro. Some of the guys flying speed limit combat around here use LA .25's and 30% Helicopter fuel - I have much better luck with Magnums. I've had two LA .25's to play with but they were inconsistant. One ran OK, the other was slow and never did get up to the speed limit, no matter what we did to it.
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Old 08-15-2010, 11:06 PM
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Default RE: OS .25FP Any good???


I use a iron piston .25fp on my flitestreak ARF and it has plenty of power. All of the FP series are good running engines.
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Old 08-16-2010, 07:48 AM
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Default RE: OS .25FP Any good???

Add 8 oz. of castor for a LA 25
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