My first Fox RC engine was Fox Eagle I, purchased in 1973. I flew it for a few of years and was very happy with it. Circa 1976 I crashed the plane it was in damaging the engine which I then sent off to Fox for service. When it came back, it had the new (at that time) MK X-B carb on it. It had no instructions for the new carb and the carb needle valves were in a seperate package. Since at the time I had a couple of new Enyas I was flying, I packed away the engine. Well, it is now time to get it out and put it back to work. Now for my question. Does anyone know what the initial settings were for both the low and high speed needle valves on the MK X-B carb? I am most interested in the initial low speed needle valve setting.

Konrad, I too would be interested in seeing the modifications of the MK X-B low speed needle valve for improving the mid range since I may need to do that.

General comment: Last fall I bought a new .74 Eagle from Fox with the new carb on it. I have been breaking it in on the test stand and it has performed great. I really like the new carb. I will be puting it in the new GP Escapade 60 when it arrives, hopefully at the end of January. If it performs in the air as well as I expect, I plan to get a second one for the Ultra Sport 60 I am building.

Bruce

When I get home I'll take a photo of the mods to the low speed mixture needle. As to the initial setting for the mK x carb there is no such thing. Duke had no idea as to the fuel you were going t use, the tank placement or the weather conditions.
Duke does say to set the needle detents circular disk on the needles with in 1/16 of an inch of the to the tips of the needle retention clips. I just prime, turn and burn!

I have to say I'm a little surprised at how few folks know how to fine tune a twin needle carb. This isn't just a Fox issue but any true twin needle carb. Again, this is not unique to Fox,

All the best,
Konrad

Konrad first you tell me there is no initial setting and then you give it to me:

I know how to tune an engine, I have been doing it for 54 years. It is just easier if you have a recommended starting place.[:-]

Bruce

We need to get back on track about Fox engines. This isn't the place to start concentrating on the deficiencies of another brand.

You know, I never thought about adjusting a Fox carb by using the number of turns out. Using a engine test stand; usually I set the idle to around 1 and 1/2 to 2 turns out, then the main needle way out like at 5 turns. I fire up the engine, run it extra rich for a while to get it oiled up good on the inside, usually around 6 to 8 thousand RPMs or so. You may have to leave the glow starter on it if it is way to rich at first. I then lean it out a little. next I adjust idle to get a decent idle, then I go back to the main jet and adjust it. If you are breaking it in, you'll need to run it on the rich side for a while, sometimes a long while. You may have to repeat the process a few times depending on if the engine is breaking in or not. Generally, for the FOX engines with the older carbs, you set idle first, an then adjust the main jet needle. The idle jet can affect the main jet. But normally once you get the idle dialed in, you rarely need to mess with it again for a long time.

I have a Fox 74 Eagle IV with the EZ carb (single needle, airbleed idle adjust). I have not started it yet (bought it used) and have never owned or operated a Fox or a single-needle carb. Do I adjust the high speed needle first? Or do I work on the idle adjustment first?

I would simply turn ther high speed out a few turns and fire it up. Then let it run extra rich for a while at lower RPMs to get it lubed up good first, then start leaning it out some. the idle adjustment on the EZ carb doesn't affect the high speed adjustment, so after you have it running Ok on the rich side, then tweak the idle adjustment. Then just in case, check the high speed again too.

Thanks, that's easy enough.

As promised here is a photo of the Fox manual. If this doesn't answer your question I can draw the needle and its relationship to the metering orfice (spray bar when I get back to Everett Wa.. Right now I'm at home with family in San Francisco and while I hate to say this I do place a much higher value on my family than I do my friends here on RCU.

All the best,
Konrad

We are on track, never left. We were talking about how great the FOX is, in not needing nitro to run properly. Now unfortunately for better or worse OS is the defunct standard that most novices are familiar with. The mention of OS is not so much a discussion about her deficiencies but rather a starting point to help anyone get a better understanding of how an engine should tune. OS is the base line, or as I like to think the lowest common denominator. This is actually a good thing for OS as it is an admission that she has market dominance.

Our valued member mentioned OS as his frame of reference. How is one to avoid this and best serve his need to understand how engine run be them a Fox, OS or other brand. I agree OS doesn't deserve a mention in this form. But unfortunately she is the norm at the field.

All the best,
Konrad

As most of you know I prefer to use lithium as my power source for the 21st century. As such most of my glow information and engines have been crated up and placed in storage a long time ago. As such I have to apologize for taking so long to find and post this asked for information about the last production run of the FOX baffle 0.78. This is from an article by Peter Chinn. Lets see if these Fox 0.78 power plots will post. If it posts I'll come back a write my observations with the engine and a little of what Peter Chinn wrote.
For those that like prop rpm here is some of what Peter Chinn found, again this was with rational fuel 80/20 (NO NITRO!) and stock Fox muffler.
The prop was a Top Flight maple.
TF [email protected] rpm
TF [email protected] rpm
TF [email protected] rpm
TF [email protected] rpm
TF [email protected] rpm
TF [email protected] rpm

All the best,
Konrad

All auto mixture type carbs with an air bleed idle adjustment should be adjusted with the air bleed closed. If and only if there is hesitation or an adjustment is needed at idle for tank placement should the air bleed be opened. The Fox Easy Adjust carb is an auto mixture type carb but with a fixed metering slot and position. There is no cross talk with the Easy Adjust carb at full throttle.

Not that Fox has ever used an air bleed type carb but they too should be set with the air bleed shut. And if possible the tank placement be adjusted to gain the desirable idle mixture. Failing that the air bleed should be opened to get the best engine response. Remember that any air that is bleed is not contributing to the fuel draw from the tank. With the low air flow at idle the engine need all the help it can get to bring the fuel to the engine. I can't stress enough the need for proper tank placement no matter the engine brand, carb type or plane used. Most ARF trainers place the fuel tank too low.

Opening up the air bleed limits (deteriorate) the engine's ability to draw fuel fuel from the tank. This is why the Fox line of engine is so superior to some of the popular asian brand entry level engines. As all Fox RC engine come with an auto mixture carb of some sort, even the little Fox 0.15 BB R/C. They all draw fuel better than any true air bleed carb at idle. This alone is worth the extra effort some FOXs need in giving them 20 minutes of your time and fuel to break them in. There are a lot of other benefits to the Fox but that would be called piling on by some .

All the best,
Konrad

Bruce,
I still stand by my statement that there is no initial setting. Now in the interest of full disclosure I felt I had to give you what Duke wrote in the manual[X(]

All the best,
Konrad

I don't understand why you constantly have to keep picking on other brands all the time, are you even running any of the small glow engines yourself?
There are even engines that are smaller in capacity then the Fox .15, they are made in asia, feature true ABC and have twin needle carbs etc.

Back to Fox, there are two obvious design flaws on the .15BB model as I see it. The head with a poorly fitted regular glow plug, and the poor design in the inlet area of the crank (ends forward with the threaded prop bolt). It is still a fairly decent sport engine though. The best running engine on 80/20 that I have seen in this size-range is the Webra 1.8cc Speedy, but it also features a glow head rather than a glow plug.

On all my engines with an airbleed type carb, the air bleed port is closed to the outside world by the design of the throttle barrel at any point other than idle anyway.

I mentioned no brand. So how can I be constantly picking on other brands? I do bring to the forefront the limitation of the products/designs regardless of the brand. I do this in an effort to increase the understanding of the product/design. The more someone understands the product/design the better it can be utilized! I mentioned "popular Asian" as a way to encompass the entry level engines from Enya, Thunder Tiger and OS. All three manufactures make entry level engines with true air bleed carbs. Again I wasn't trying to single out any "BRAND" I am aware of many fine engine from all around the world that are smaller and even more advanced. I'm thinking of engines build for the FAI F1J 1cc class.

Back to the FOX why pick on her? Most engines have the crankshaft bore machined to a flat bottom. It cost more money to sharped a fully radiuses cutter. I think I mentioned these issue before in this thread. Rossi and many high performance brands have been using radiused cutter for a long time. ( I'm writing up a post to show the how of the FOX 10 cc crankshaft from the Hawk to Eagle IV. I will cover this in detail) As to the head, Fox has made many head shapes for the little 15 BB. (I liked the FAI High Compression trumpet head) The issue you state is common to most FOX heads. It was done on purpose to allow the user to custom fit (lap the glow plug seal area) to ones desired fit. This is a much better way to accomplish the desired placement of the glow plug than the use of shims under the glow plug. There really is no defined definition as to what is the "best" fit. But we can agree with a lot of what doesn't fit. We agree that the "glow button head" is superior. I also like the Nelson/Glow Bee tapered sealing glow plug arrangement.

All the best,
Konrad

That is how they work. The placement of the hole determines at what point in the throttle position it is opened or closed is going the other way. The air bleed does effect the fuel mixture at other positions other than just idle. It effects the mixture at idle and off idle until the barrel closes the port.

Now one of the benefits of an auto mixture carb is that the fuel orifice can/does control the fuel much better at throttle position other than full power (more on this latter).
Because of this superior ability to control the fuel flow the engine designer can make an engine with great flow capacity, both in port area and timing. The air bleed carb is limited in its ability to deal with any radical flow reversals at low speeds (idle). Now because the auto mixture carb can deal with more radical air flows at idle it affords the designer an opportunity to give us engines that a more powerful yet track/handle better. While it is true that for any given choke are both carbs will allow the engine to perform the same at full throttle. The engine and carb need to be looked at as a system. With the auto mixture carb the engine designer can give use a more powerful engine that actually idles better ,is more flexible and has more power. The true air bleed today is only on the market as a cost saving device! Duke has always avoided the true air bleed carb in an effort to supply us with only the best!

Hey, it is a pro Fox thread after all!

All the best,
Konrad

Konrad, thanks for the info. Unfortunately, the plane my engine is installed in gives no ability to adjust the fuel tank location. So, I'll most likely need to mess with the air bleed adjustment.

That is why Duke provided it.

All the best,
Konrad

I went out to get in a few flights today to start off the New Year good. So here is a rare photo of myself with a RC airplane.
This is a Tiger 60 airplane with a Fox 60 Blue Head dual plug engine made circa 1966. It was pretty chilly outside today, so I had some trouble getting the engine to start up when cold. But once I got it running and warmed up, everything went smoothly. I needed to go a few clicks out on the needle valve to compensate for the denser air as well. If you missed my earlier posts about the engine here in this thread, I adapted a Davis DieselDevelopment .60 to .90 size SoundMaster muffler to work on the engine. Basically I only opened up the exhaust inlet in the muffler a little bit and of course I needed to remove the exhaust baffle on the engine too. I made a couple of small aluminum plugs for the holes left in the engine where the exhaust baffle went. The muffler clamp holds the plugs in place.
The plane is a lot less messy, now that I got the muffler to stay on and not come loose like before.

Earl,

Very nice.

Earl,
Here is a very very rare thing to behold. A WORN OUT FOX!
NO amount of re-ringing or even honing on my part can bring this sleeve back to serviceable condition.

Note that because Fox pins the ring to the piston it did not rotate in the cylinder.
This allowed the ring to wear in one spot causing what looks like a bump where the ring gap was.
The wear under the yellow line is 0.0022" in diameter. All but 0.0002" of that is on one side under the ring gap!
I would have to hone the cylinder close to 0.004" oversize just to clean up this wear.
I'm pretty sure that at that size I would break through all the nitrated steel and be well into the soft leaded carbon steel.

All the rest looks good. Of course it would it is a FOX! The Fox is a great sport engine with a nod to being more!

This engine was run for 4 years on none castor oil fuel with 5% nitro. The brand name was a local brand called BK hobbies.
While the guy who owned the engine did use ATF as an ARO I was surprised at how little rust I found in the engine. and this was after 4 years of hard running with about 120 oz of fuel run through it every week all year long. I can attest to the fact that the engine was run hard and at times lean! It still ran good, but not as good as new. It just needed an electric starter to start reliably.

This is the engine I parted out for your Eagle II upper cylinder casting.

All the best,
Konrad

Nice to see you on the screen, Earl.

Which model is that?


Ed Cregger

It is a copy of a Goldberg Tiger .60 RC plane.
Thanks guys

I am impressed Konrad, it looks like someone ran a lot more than a 100 gallons of fuel through that engine to get that much wear. I honestly have not worn out any Fox engine yet. Although I came close with my old Fox Hawk .60 though. But new bearings and rings and it is back up to snuff.

The poor guy was trying to keep up with me (poor fool). As a result the engine did see a few lean runs!
Here is a peak at what I hope to post about Fox's 10 cc crankshafts I show a 40Q just for reference, a Hawk, and Eagle I, Eagle II/III and an Eagle IV. You will note that they all have,what one OEM is now trying to say is new in their ads, and that is a balanced "D"-cut crankshaft supported by dual bearings, or derivation there of. (I have to thank BW for bring this term, "D"-cut crankshaft to my notice) The Eagle I and Hawk cranks are from the 70's, far from new in my book! This was the first time I have had an Eagle IV apart. And WOW was I pleasantly surprised! Notice that the Eagle IV and 40Q crankshafts has an ear of the "D" cut off opposite the cut out for the inlet port. More about the Eagle IV and the cranks later!

All the best,
Konrad