Which Fox 25?

A friend has loaned me a box of several older engines to play with and test on my stand while I'm mending. I may buy one to put on my Flite Streak ARF. These include a Fox 15, Stallion 35, McCoy 19 and 25, and a Fox 25. The Fox 25 is the subject of my question. On the side it says, "Fox 25 RC". The carb has been replaced by a venturi which is mounted on a flat plate on the motor and is secured by 2 small screws. The venturi does not lean forward, but sits straight up, parallel to the cylinder. The engine seems to be in excellent shape with good compression and no obvious "clicks" or "rubs" when I turn it over. No rust, and by the way it smells, it was stored with a good lubing of after-run oil. I haven't run it, yet, but I don't know why it wouldn't run well.
Question: Does anyone know during what time frame this engine may have been produced, and what would be a fair offer for the engine?
I emailed Fox, but haven't received an answer yet. Thanks for any advice.
Glen

The only people I know with experience with this motor are Paul Taylor ("rootbeard") and his sons. He might give you some insight as to how it performs. dg

Glenn, that engine is a good power house for a Skyray 35, but in my opinion a bit weak for a Flight Streak. It likes to run in a rich two stroke. Fox Mfg still has a good supply of parts for that engine as do a lot of individuals such as I.
I think it was produced in the 70s and 80s. It needs a lot of castor oil but likes 10 t0 15 percent nitro 25 % oil at least with most of it castor. Unlike the stunt 35, it has plenty of cooling fin area.
A 10 X 4 or 9 X 5 prop should do quite well on that engine.
Price?? $15 to $25 would probably be a bargain as it is apparently new, or nearly so.

Good luck and keep us posted.
By the way--- Are you sure the McCoy that you list as a 25 really is a 25?? I have never heard of a McCoy 25 . Sure it is not a 29 or 35?

Bigiron

You're right, the McCoy is a '29. I experienced a cranial cramp. Thanks for the advice. My friend has told me that a '35 is probably too much for the FS ARF since it is extremely light. I have a Fox 35 that I had planned to run in the plane, and I think the hole spacings are the same for the 25 and 35, just by visual inspection, which, I know, isn't that reliable. If they are interchangeable, I can try one and then the other. Should be a fun experiment, but first, I need to put the 25 on the stand and see how it runs. Thanks again!! Glen

Your in Luck,
The Fox 19,25,29(stunt) and 35(stunt) all have the same mounting holes.

I agree with BigIron, the Fox 25 is a bit weak for a Flite Streak. Try the Stallion 35 on the Flite Streak. It's not a stunt engine, just a good sport engine to run in a 2 cycle mode. A good match for the FS.
I run a Fox 25 (4 bolt backplate, 70's vintage) on a Tomahawk, which is a bit smaller than a FS.
Happy Landings

Hi Glen,
We put one of the bolt on venturi Fox 25 on a TF kit Flite Streak as my son's first "Big" plane about 12 years ago. Used a 9-5 prop, ran it in a wet 2 cycle, and that's what he learned most of the stunt pattern with. Seemed to fly the streak pretty well, even after having to replace the case twice. But it wasn't "overpowered".
Bill <><

Thanks, Bill:
I'm going to give the 25 a shot. The Stallion 35 was suggested, but the one my friend loaned me is so big and beefy and the ARF Flite Streak is SO LIGHT, I don't know how it would work out. Also, I'd have to carve out a lot of the mounting blocks just to get it in there.

This is for everybody who participates in this forum. I can't begin to thank everyone for the help, advice, and general knowledge I've gained from all of you. Getting back into model airplanes literally gave me a new life. As far as skill is concerned, I'm nowhere near most of you, but that doesn't seem to matter to the "brotherhood", so to speak. As I recover from my heart surgery, this forum helps me keep on looking forward to the future, which if I can get my blood pressure under control and regain a good sense of balance, will include many fun days of flying in circles. Thanks you all!!
Glen

Glenn,
Sounds like we have an engine just like yours. As everyone says it likes to run wet with lots of castor. 29%.
It seems to be a good runner. Not sure on the power. We have it on a Flite Streak Trainer. The plane is a little bit of a porker due to repairs and my lack of building light. My son has done inside loops, wing overs and seems to track nicely with tight lines. I am sure he will try 8's with it over Christmas break.

All in all we are happy with it on the FST.

Get well soon. Spring is right around the corner.

Merry Christmas
Paul

Glen,

Best for quick and good recovery!

I've found that Fox 25 a bit of a shaker if you try to lug it. A light-load 9-5 should get it into a sweeter RPM range.

Nice power, easy/dependable starting, on the ~25% castor and ~10% nitro already recommended.

Enjoy!

Don't be afraid to try an 8x6 or 9x4 prop.

My luck, I finally find a flying buddy that does not live in Dallas, Houston, Pampa, Arkansas, or..., and his heart starts acting up!! I know my flying is scary at times, but I did not think it would cause a heart attack! Get well soon Glen.
SPITFIRE ( in Aggieland )

Thanks, Dale:
It certainly wasn't your flying; your flying is a joy to watch, and it is an honor to have you as a flying buddy. Hopefully, I can start flying with you in February. Thanks again for your friendship.
Glen

Fired the Fox 25 up a few minutes ago. Had to use a starter, as I didn't realize I had it too lean. It must be broken in, as it held a screaming 2 cycle without sagging until I, in a state of befuddlement, figured out what was wrong. Seems like ST NVA's need to really be cranked out. It ran at a nice wet 2 cycle at 3 and 1/2 turns. I shut it down after about a minute and tried a hot start with the chicken stick. It fired on the first flip. I ran it on GMA 5/29 all castor with an OS A8 plug. This was the first I had done anything with model airplanes since my heart surgery, and it really felt great. I finally have some energy!!!
Glen

Nice.....
And the sweet smell of nitro.

Gett-er-done!

Paul

The one thing I don't like about the Fox 25 is the front muffler mounting lug making it difficult to choke. I've got one I never plan on using a muffler on so I sawed off the lug.

Hi, Elwin:
I know what you mean, but this engine doesn't have any lugs. It is an RC engine converted to CL. It has been drilled and tapped at top center and bottom center of the exhaust outlet. These are tiny holes, and I THINK they are for a baffle for idling. Some old RC engines had either a butterfly or shutter type baffle that was linked to the throttle to close off the exhaust as the engine was idled down. Supposedly this increased back pressure and improved idle. I had a dual-plug Merco 61 RC that had a butterfly baffle, and it had an idle and throttle response that, as I recall, nothing I've seen recently could beat. I emailed Fox asking about the little holes, but no answer yet. These older engines are really interesting. Thanks for your input.
Glen

LAST EDITED ON Dec-16-04 AT 09:40 AM (CST)
 
Glen,
I have that Fox .25 in both CL and RC. The RC is as you describe. The exhaust has a baffle that rotates in those holes. The muffler is a flow-through type and is notched to miss the baffle. The muffler is held on by screws above and below the exhaust. The throttle is linked to the exhaust baffle.
The CL version says RC on the crankcase but does not have the exhaust baffle holes. It too has the muffler attached by screws above and below the exhaust.
That would indicate that yours has been converted from RC...unless Fox did a mix and match.
Neither has the fore and aft muffler ears.

George

Edit: After re-reading your posting, you may be referring to the muffler mounting holes. The exhaust baffle on the RC is a barrel type with holes drilled fore and aft in the exhaust stack.
Edit2: Aw heck, a pic is worth...

Glen: 3.5 turns on a needle setting is not "really cranked out" at all. This is about normal. Currell

Hi George,
Our first was an RC that I got the venturi for. When that crankcase broke, Fox sent another with the RC but no holes for a baffle, after THAT crankcase broke, Fox sent what I guess by then was the C/L case.
IIRC, it is a matt finish with the dog ears like a 40th Anniv. Fox 35.
It still starts, runs good, and has plenty of compression.
Bob Hunt used one of these tuned by Tom H. in his Frisky Pete.
Bill <><

Bill,

I saw Frisky Pete in Bob's SFVM. I wonder if he ever had time to complete the plans for publication?

I liked that plane. I remember Bob mentioning in the video that you need to consider the motor mount position since the original engine had the higher offset mounts and most, if not all, current engines have centered mounts.

Hi George,
I am pretty sure Bob has those plans available now.
IIRC, the original plans had an O&R 23 which had the thrust line/mounting lugs offset which he corrected on his plans.
Bill <><

Bill,

When you say the crankcase broke are you referring to the venturi mounting flange?
Combat flyers had quite a problem with that on the Fox .15 schnuerle. Someone (Isky?) mentioned using nylon screws to attach the venturi so it wouldn't ruin the case.
From your description, I guess both of mine are the older models. They have the shiney case with no muffler ears.

George, the cases broke on the bottom. Mainly where the mounting lugs are cast, both times. Aaron drove them in pretty hard! hahahaha
My first one was like the R/C you show, 1st replacement case was like your C/L, last case was the "matt" one. Crank/rod never got bent!
Bill <><

Hi, George:
Thanks for the pics. The one I have is exactly like the one on the right. Thanks, again. Glen

Hi Glen,
There was/is a Fox muffler to mount on the two vertical lugs available.
Bill <><

I purchased a tongue muffler from some after market guy. Perhaps it was our host Leonard. he or Big Art A.

Bigiron