Author Topic: Breaking-in Fox.35 (Read 7488 times)

Paulo Turini · « **on:** March 13, 2009, 06:08:38 AM »

Good day everyone

I am newbee to the hobby. Bought a Fox.35 15 years ago when I intended to start, but it was postponed.

..till now.

well i took the fox.35 out of the box, for a new plane i am buillding, and i am wondering if you guys could give me a guide how to break-in the engine. I've read the recent post comparing the OS.25 and the Fox.35, maybe I should give the engine a try? http://stunthanger.com/smf/index.php?topic=11149.0

tks

Paulo

Ralph Wenzel (d) · « **Reply #1 on:** March 13, 2009, 07:50:40 AM »

Before you begin breaking in the engine, remove the head and backplate and thoroughly flush the engine with kerosene. Foxes are notorious for having small pieces of metal from the manufacturing process, and they can quickly ruin your piston and liner.

Choose a balanced 8-5 or 9-4 prop and mount it securely, along with a fuel tank whose top is about level with the needle valve. Don't fill the tank yet.

Prime the engine and flip a few times. Then hook up the battery and flip . . . and flip . . . Reprime and flip, etc. You are learning what procedure the engine likes for starting. Once you can prime and get the engine to run out the prime a few of times, fill the tank with fresh 10% Nitro, 29% Castor Oil fuel. Choke a turn or two - just enough to get fuel to the end of the spraybar. Close the needle valve, and then open it about 5 turns. Prime, flip, hook up the battery and flip again.

When the engine starts, go around behind the engine so you can safely adjust the needle valve. You want to set the needle so the engine is running right on the edge between a fast 4-cycle and a rich 2-cycle. Let the engine run for 30 seconds and then pinch the fuel line to kill it. Let the engine cool completely, and repeat this cycle about 10 times. You are "heat cycling" the engine, which allows the sliding and rotating parts to mate gently. Extended runs do not accomplish this (except perhaps very slowly).

Then increase the run length go 1 minute, and occasionally pinch the fuel line momentarily to produce a full-throated 2-cycle run. Pinch off the fuel line after 1 minute. Repeat this cycle about 20 times.

Then increase the run time to 2 minutes, for about 10 cycles. Then to 4 minutes for 10 cycles. And finally to 6 minutes, pinching the fuel line often to produce that 2-cycle run. When the engine will break into the 2-cycle run for about 15 - 20 seconds, and then drop back immediately to a 4-cycle when you release the fuel line, it can be flown. At this time, replace the break-in propeller with a 10-6 or 9-6 for flight. (THe 9-4 was only for break-in.)

This entire procedure, so far, will require approximately a gallon of fuel. For all flights, be sure the engine is set rich enough that it will not go into a sustained, lean 2-stroke run. Be prepared to replace the Glow Plug, as break-in is a period of high stress for all working parts of the engine. IF the engine doesn't respond to its normal starting procedure, something is amiss. This is why you "wasted" all that time getting the engine to run out the prime, but with no fuel in the tank.)

Always have a fuel filter in the fuel line. It's a good idea to have an air filter over the venturi, also. This can be as simple as a couple of thicknesses of pantyhose held on with a rubber band. Always replace the cap on the fuel can; Methanol attracts moisture from the atmosphere.

Others will offer additional suggestions and procedures. There are other ways to do it; this is just what I do.

GEOFFREY · « **Reply #2 on:** March 13, 2009, 08:10:41 AM »

find some Sig 10/25 all castor fuel. add 4 oz castor to this.. mount on test stand and mount a 11/5 prop and start flipping. let first run be very wet 4 cly 3 min. let it cool down make sure that the piston is down when it is in cooling mode. when cool start again repeat at least 6 times .. then as it is running pinch fuel line for a second it will 2cly for just a burp do this for the next 6 runs. by now you should see the top edge of the piston becoming very shinny. and it will be starting on 1 or 2 flips.. turn needle in a turn and fin right st the spot when it breaks to 2 cly and back out to smooth 4 cly . i would run on stand until the gallon is 3/4 gone or mount and fly with out stressing with a full stunt pattern.

john e. holliday · « **Reply #3 on:** March 13, 2009, 09:01:51 AM »

I am from the old school from way back when I was a member of the Flying Eagles. I would put the engine on the bench with a 9-6 prop. Use the fuel I am going to fly with. Now it is any well known brand that is 10% nitro with at least 22% oil half and half castor and synthetic. If the engine is tight I prime as stated and flip a few times. Adding another prime after so many flips. Then hook up battery and see if I get a bump. If I do I flip the prop to see if its going to start. If it starts and runs out the prime, I fill the tank, prime engine, flip prop. Usually the prime is enough to get fuel to the engine. Yes the needle is opened up about 5 or 6 turns from close. Sometimes I have to let the first tank or two run with battery hooked up. Depending on how tight the engine is and the needle setting it m ay take a minute or two to get the engine thoroughly warmed up. When I get the engine to run steady with what I call a flying setting, it goes in the plane. When it does go in the plane, make sure needle is a little rich and only about two ounces of fuel. The last couple of laps it should lean out. This is my way with a Fox .35 Stunt. I have some that are over 30 years old and still strong as ever. The ones I run in Foxy racing are a different story. Have fun, DOC Holliday

Andrew Hathaway · « **Reply #4 on:** March 13, 2009, 10:58:01 AM »

Pull the rear cover, hook the short end of an Allen key behind the connecting rod and see if you can slide it back and forth on the wrist pin. They have a habit of getting stuck if they sit for any period of time. If it won't slide, heat it up with a monokote heat gun till it will. When you reinstall the back plate, you may want to apply RTV to both sides of the gasket.

Cut a piece of fuel tubing about 3/8" long, and slip it over the needle so it seals from the bottom knob to the top of the spray bar. While you've got it out, take note if it's the later full taper needle or if it's got a flat spot on one side. If it's the flat spot needle, you may want to upgrade to the new style needle. Both will work but the later needle is easier to set.

Mount the engine in a test stand with a 9x5 or so wood prop, make a few short runs. When it reaches the point where it'll start without much trouble, bolt it on a Bi-Slob, Ringmaster, Flite Streak, etc and fly it a bunch. After many flights the engine will be broke in and ready for a more serious plane. It's much easier to deal with out in the open, then upside down inside a cowl.

If you want instant gratification, an OS 25 will run the same after a few runs as it will after 1000 runs. The Fox just takes a good while longer to mature into itself. The Fox 35 will never be a modern engine, but it'll run as good as any Fox 35 ever has. At least you'll never have to worry about replacing the plastic backplate, or the remote needle, or the silly screws.

Paulo Turini · « **Reply #5 on:** March 13, 2009, 11:18:12 AM »

Quote from: Ralph Wenzel on March 13, 2009, 07:50:40 AM

Before you begin breaking in the engine, remove the head and backplate and thoroughly flush the engine with kerosene. Foxes are notorious for having small pieces of metal from the manufacturing process, and they can quickly ruin your piston and liner.

The engine was completely stuck so I opened it up and let if few days immersed in kerosene to clean it. after that parts were released and i lubed it with wd40 oil. Yes, indeed a LOT of small metal dust came out...one thing else, the back plate gasket is ruined after so many years... It will be tough to find spares here in Brazil. Can I replace it using some alternative material?
Tks all for the leads!

Alex Givan · « **Reply #6 on:** March 13, 2009, 11:51:11 AM »

How about Lustrox? I have heard that you can mix a small amount of this in your fuel and this will break in the engine. Is anyone out their familiar with this stuff and if so what is the best way to use it. How much should you use to mix a batch of fuel for this purpose? Also I have heard that you can mix some with a light oil, put a few drops in the intake or a few drops in the plug hole and use a drill to drive the crankshaft. Has anyone heard of this product or any of these methods?

john e. holliday · « **Reply #7 on:** March 13, 2009, 11:55:42 AM »

Yes I have heard of it. The problem is if you are not careful you can ruin a good engine in no time. I have taken old Foxes of mine that were loaded up with burnt castor and use real fine lapping compound to clean the piston cylinder. DOC Holliday

Dave Rountree · « **Reply #8 on:** March 13, 2009, 01:30:22 PM »

Paulo olny like to add to the above info, i dont like to pinch the fuel line to shut it off. it leans out the motor ( to soon in the break in process ) i like to richen the needle until i flood it to death. but that is just my thought. Dave R

Alex Givan · « **Reply #9 on:** March 13, 2009, 02:23:58 PM »

Thanks Doc-
Can you or anyone else go into a little more detail about breaking in a Fox in particular with the use of Lustrox? I have ordered some of this stuff and would like to know all about it before I go and make a mistake by being to aggressive, or not knowing when I have it just right and should stop. But if I go to far it will give me an excuse to order a ceramic piston/liner as a replacement and give that a try.

Tom Rounds · « **Reply #10 on:** March 13, 2009, 03:11:55 PM »

Where can you get Lustrox? Does Fox still offer it?
Thanks,
Tom

Alan Hahn · « **Reply #11 on:** March 13, 2009, 03:19:48 PM »

Quote from: Paulo Turini on March 13, 2009, 11:18:12 AM

The engine was completely stuck so I opened it up and let if few days immersed in kerosene to clean it. after that parts were released and i lubed it with wd40 oil. Yes, indeed a LOT of small metal dust came out...one thing else, the back plate gasket is ruined after so many years... It will be tough to find spares here in Brazil. Can I replace it using some alternative material?
Tks all for the leads!

I have used automotive gasket material (a paper-like material~0.9mm thick) to seal up the backplate. First cut out a piece larger than the backplate. Use the backplate itself as a pattern to cut out the inner circle/hole. Slide the backplate into the resulting hole, use a sharp pointed tool to poke 3 holes where the backplate screws go. The mount the backplate and tighten the screws--don't overtighten though. Now take a razor blade, or an exacto knife and trim the outside of the gasket to match the Fox backplate area. It has worked fine for me.

Alex Givan · « **Reply #12 on:** March 13, 2009, 04:04:22 PM »

Quote from: Tom Rounds on March 13, 2009, 03:11:55 PM

Where can you get Lustrox? Does Fox still offer it?
Thanks,
Tom
[ Yeah! Fox sold me some this past Tuesday, I have yet to receive it but will give it a try as soon as it arrives. Hope to get some solid advice on this stuff before I try what I feel may work. I have Three McCoy's that the piston falls under it's own weight but has very tight compression at the top of the stroke, all Three start and run flawlessly. My McCoy's are outstanding engines and I may try to get the same feel with a Fox, as this seems to be what everyone is striving for./quote]

Neville Legg · « **Reply #13 on:** March 13, 2009, 04:26:13 PM »

I thought I read somewhere that the Fox requires a minimum of 28% oil, preferably Castor!

Cheers Neville

George · « **Reply #14 on:** March 13, 2009, 04:45:35 PM »

Quote from: Alex Givan on March 13, 2009, 11:51:11 AM

How about Lustrox? I have heard that you can mix a small amount of this in your fuel and this will break in the engine. Is anyone out their familiar with this stuff and if so what is the best way to use it. How much should you use to mix a batch of fuel for this purpose? Also I have heard that you can mix some with a light oil, put a few drops in the intake or a few drops in the plug hole and use a drill to drive the crankshaft. Has anyone heard of this product or any of these methods?

Alex,

You do not mix it with fuel unless it's to be able to dispense it with an eyedropper. Duke Fox used to recommend just dabbing a little in the intake. You only do this ONE time, it is not to be run in your fuel. Although I still have a little Lustrox, I prefer to just use heat cycles. I think Lustrox is more for speedy break-in, not necessarily BEST break-in.

But this is just one opinion.

George

George · « **Reply #15 on:** March 13, 2009, 04:49:28 PM »

Quote from: Paulo Turini on March 13, 2009, 11:18:12 AM

...one thing else, the back plate gasket is ruined after so many years... It will be tough to find spares here in Brazil. Can I replace it using some alternative material?
Tks all for the leads!

Paulo,
You can use playing cards to make backplate gaskets.

George

ray copeland · « **Reply #16 on:** March 13, 2009, 05:52:08 PM »

My friend that has been flying Line Control for 50 years just kinda grinned when i mentioned Lustrox and said yeah, it used to come packaged with new Fox's and we used to just swab it on the intake one time, run a tank of fuel and go flying. But he really couldn't tell me if it helped or hurt. Said they seemed to run fine afterward..

Andrew Hathaway · « **Reply #17 on:** March 13, 2009, 08:15:35 PM »

As I understand it, Lustrox = powdered cleanser... i.e. Comet, Bon Ami, etc. It's an old school shortcut intended to speed up the the wear process. I wouldn't try it, but that's just me.

Bill Adair · « **Reply #18 on:** March 13, 2009, 10:47:22 PM »

Perhaps I'm old fashioned, but I just can't see using an abrasive to accelerate the break-in of an engine!

Sure, Fox iron piston engines are a pain to break-in, but will last nearly forever when done properly.

Bill

Clayton Berry · « **Reply #19 on:** March 14, 2009, 11:57:38 PM »

Find stack of important or semi-important papers on desk. Place Fox on these papers for at least a day or two. Find stack of cash. Place on desk. Lift Fox 35, and place on money. Two days. Get menu from diner in NC that has livermush as an item. Use black magic marker to high light it, and position Fox 35 over it. Leave it forever. It are broken in.

Some people would have you believe you have to run them and use certain fuels and props. They sell fuel and props. Always follow the money. Millions of dollars have been spent breaking these things in, and yet there is a simple method that costs virtually nothing. Newton's gravity. All you need to know.

George · « **Reply #20 on:** March 15, 2009, 09:31:39 AM »

Quote from: Andrew Hathaway on March 13, 2009, 08:15:35 PM

As I understand it, Lustrox = powdered cleanser... i.e. Comet, Bon Ami, etc. It's an old school shortcut intended to speed up the the wear process. I wouldn't try it, but that's just me.

I thought it was aluminum oxide. Your guess is just as good...perhaps better...than mine.

George

Jim Kraft · « **Reply #21 on:** March 15, 2009, 12:37:29 PM »

The problem I have with running any abrasive through the engine is that it also wears the rod, wristpin, and crank bearing at the same time. By the time you get the piston cyl. fit, the rest of the engine is worn out, although some engines it would not hurt to loosen up everything a little. If I wanted to hurry the breakin I would lap the piston/sleeve a little before I would run any abrasive through it.

Robert Zambelli · « **Reply #22 on:** March 15, 2009, 02:19:50 PM »

One of the guys from Fox told me that Lustrox was nothing more than white jeweler's rouge.

We have been breaking in and running Fox 35s on 10-23 50/50 castor/synthetic for years - never a problem.
I run Brodak 10-23 exclusively no matter what kind of run I need. I have hundreds of flights on my Stinger and I run it screaming lean on a 9 1/2-6 prop.
On my Nobler, I run it in a classic 2-4 and a 10-6 props. Same fuel, excellent runs.

Also, I have run this same fuel in very old engines including two-bolt Foxes, slant plug and green-head K&Bs and my Atwood Triumph. Again, never a problem.

Bob Z.

Author Topic: Breaking-in Fox.35 (Read 7488 times)

Alan Hahn