I have the standard Fox .049.  I broke it in for about 1/2 hour and it would hold a steady 2 stroke at the end. I am using 15% Nitro fuel and a 6x3 prop. It sounds great on the ground and initially in the air. However, on my Lil Geo it has arbitrarily quit all three flights. Twice inverted, causing damage both times.

Does anyone have experience with this engine that would indicate that I should do something different?

Tee Dees I got, and know how to run.  I want this airplane to fly with the Fox!  I worked for Duke for a while, and it is a nostalgia thing.  I don't want to run .35s (I have an outstanding one, Ceramic liner L&J), and the .15 seems hopeless for consistency.  The .07 and .09 are strange.  So the .049 is it!

Excellent input!  Thanks.  I have a lathe..... 

             This isn't a plug related problem is it Larry? I had a .07 that was giving me similar fits. I would take the plug out and it would glow fine. I replaced it and problem solved. The real problem is the rarity of the plug. Ken

Hello Larry,
Treat yourself to a Mattes Rework adapter ring, then you are good to go with a whole range of plug/head combos or even a Cox head. I suspect you won't regret it.

Regards,

Andrew.

Hello Larry,
Why not talk to Doug Martin about your problem. He is the guy that assembles them these days. If anyone would know what the problem was, he would.
My Fox 0.49 was ,I believe, built up by Doug and despite the sneering comments of some others, it goes very well indeed and I am right pleased with it. Doug's email address is dougsengines@hotmail.com, he seemed a helpful sort of guy when I dealt with him.

Regards,

Andrew.

           I've seen many of these engines the standard .049  run and they always seemed pretty strong. I know many used them for Musciano events as well. What I did see was the crankshafts breaking. Ken

Larry, do you have any updates?  I am experiencing the same issues with mine.  I contacted Doug Martin and he mentioned someone in CA with a lot of Cox experience was having issues.  He didn't name names but I'm thinking you may know who I'm talking about  . I'm running a Merlin plug with a homemade clamp ring, 15% Sig Champion, on a BHM Flight Master. I am seeing 18.5 K on a 5/3 APC. Runs fine straight and level but dies when attempting manuevers. Doug said perhaps the nva is pointed wrong or that the Venturi is too large and needs an insert.  Sound familiar?

Hi Guys,

I have a Fox 049 of the "Comet-Repo" vintage. There are some grinder marks where the Comet logo would have been.

I am using the stock head and noticed it has just a single bypass port.

I did some bench runs on it today using Powermaster GMA blend (10% nitro, 11% castor, 11% synthetic).

Ran through a couple of tanks ok after I got the hang of starting it. Basically I had to open the needle to get her to start, then turn it in to get decent RPM's.

I am planning to pass it on to a friend for a project so I am interested to see how it works for you.

-Chris

I made a stuffer backplate, and a venturi insert to cut the flow area.  I have a Cox fine thread needle, and the hole is larger than the Fox one, and definitely in the optimum position.

How big is your venturi insert and what is the optimum position for the nva hole?

When trouble shooting my Fox .049 sport (pre-64) we found the spraybar had a really small orifice. It measured about .017" dia.

A Cox .049 reed engine spraybar measured .040" in comparison, and a Cub .049 spraybar orifice measured .025".

We had damaged the original spraybar removing it, so we drilled out the replacement spraybar orifice to .025" (same as the Cub). The Fox had refused to richen up when we first ran it, even with the needle all the way out. My friend has the same engine, and it ran almost identical to mine.

After installing the new spraybar, and sealing both sides with J-B Weld (to be sure there were no air leaks), it ran perfectly! We have not modified my friends engine like this, but suspect it will cure his run problems as well.

I realize that this could also have been caused by air leaks, but the small orifice on a relatively hot engine (for the period when it was made) just didn't make sense.

Bill

  Larry, Did I read that you were making tanks using film canisters as tanks, and using something to adhere the tubing to the plastic?

  If you would refresh my memory I sure would appreciate it...
   Thanks, Gil

Film cannisters and most small plastic bottles work fine.  The glue I use is "Goop" adhesive.

Bottles from the "travel size" section in your pharmacy or supermarket are a great source, as are some of the bottles from liquor "miniatures".  My favorite, the APS film cannisters are no longer made. 

Hmm...as time passes and technology advances we have gone to digital photos so there went the film canisters. Fortunately...or not...many of us now have small medicine bottles to replace them. :-( 

George

Film cannisters and most small plastic bottles work fine.  The glue I use is "Goop" adhesive.

Bottles from the "travel size" section in your pharmacy or supermarket are a great source, as are some of the bottles from liquor "miniatures".  My favorite, the APS film cannisters are no longer made. 

Larry, I have a couple of grocery sacks full of canisters, probably several hundred...lifetime supply and all that you know.  I hit all the photo-development places a couple of years ago when I realized they were going to become obsolete.  I'll send you some if you need them, I'll never use them all.  just let me know.

1. are you using 2 tubes to the canister ?
2. how about a photo..

Seems lately I have acquired a lot of medicine bottles or is it pill bottles.   I call it drug bottles that the doctor is pushing.  May have to try one.