blw

My Feedback: (3)

At least the spring fix works. That's the good news.

Charley

My Feedback: (2)

Duplicate, sorry.

Charley

My Feedback: (2)

That's why I said nevermind. No argument.

CR

hsukaria

What!!?? No argument?? What happened to this thread???

hsukaria

Meanwhile, I tried to bench run an old Fox 45 with an MkX carb today that ran a few weeks ago on the same bench setup. But the thing won't start. The glowplug is good, fuel good, don't know what happened.

ochsnm00

[QUOTE=carlgrover;12194948]High speed needle is not too lean. I always have a smoke trail. No amount of tuning has fixed this problem. Needles aren't dirty. I recently cleaned the entire carb. I've been tuning Fox engines for 25 years and pretty well know the procedure. I've tried setting the idle rich so it spits raw fuel out of the exhaust and still have this same problem.

You know you can use the pinch method to set the low end also. At a fast idle pinch the fuel line momentarily, if it speeds up it is rich. You don't want the low side rich, lean it and try again. If there is excessive blow-by from the front bearing the crank to the front case is worn making the engine a paper weight.

blw

My Feedback: (3)

You didn't address that comment to me did you?

aztecpilot

My Feedback: (5)

I have two Fox 50s with the older, two needle carb. Does anyone know where I can find a user manual for these engines? If not, how is the best way to adjust the needles? I don't have any real use for the engines so I might put them up for sale. - Mark

Cougar429

My Feedback: (3)

Aztecpilot, sent you a PM.

aztecpilot

My Feedback: (5)

Thanks. let me know if you do not get my reply.

Cougar429

My Feedback: (3)

You should see both the reply here and the Email.

fliteline

Looking for some Fox decals....

After being out of the hobby for almost a decade, I'm getting back in with a Dick Sarpolis Hammer .40 I'm building from scratch. I had one of these many years ago, built from the Champion models kit, powered by a Fox 45BB. It was favorite of mine, so I'm building another. It will be powered by a Fox .45BB, of course. I'm reproducing it down to the last detail, but one thing I'm missing the the Fox Power decal that I had on the tail. These small decals, featuring a simple Fox head and the words Fox Power, were supplied with Fox engines at one time and, though I still have many Fox engines, decals I no longer have. I'd like to find one of these to complete my project. Perhaps someone out there has one kicking around they'd be willing to part with?

FYI - Some of you may remember the old Fliteline Solutions website that covered Fox engines, and modifications, in some detail. I used to manage that website. So, me and Fox engines are old friends.

Regards,
George R.

Bill Adair

My Feedback: (1)

Didn't think I had any of those decals, but found 2 with a NIB Fox 25 I have on the shelf. I'd like to keep one with the new engine, but can spare the other for a good cause. Reply with your address here, or by PM if you prefer and I'll get one on the way.

Bill

fliteline

Thanks Bill. PM sent.

carlgrover

getting back to the issues I had with my Fox .50 over the last few pages.

I tried the ink pen spring fix recommended from the flightline solutions article and it didn't change anything. I still get a flame out on throttle up and it seems to be getting worse. I caught the sentence above just before I was going to close this thread and was wondering.

Just how can I tell that my front bearing is worn out? The excessive blow by could be causing my problem. If that isn't it, I'm declaring this engine the winner and conceding defeat.


carl

Cougar429

My Feedback: (3)

Does that flameout occur an fast or slow throttle ups? At what position? Cannot remember if your previous posts covered that. Did you post the carb model?

Asking as the Low Speed needle holds sway on mixture till approx 3/4 throttle, with the HS then taking over. If your engine is dying below 3/4 throttle you may have to work on the needle taper to correct for mid leaning. You're sure you have them in the correct positions?

As for front bearing issues, the 50 uses the R6N-ZZ, a double shielded unit. Not sure if anyone installed a sealed bearing in that position, but that's one solution I used in a lot of other installations. In the GMS line that was the only way to help correct their horrendous QC problem of run on and rich mixture requirement.

What starts it all is a too loose fit between the crank and case bore. This should be tight enough to be sealed with oil, but that is only effective if there is a close tolerance fit. If the manufacturing leaves that too large no amount of oil can seal. If the front bearing is shielded there is no true environmental seal and air can be drawn in when the piston is on the way up, (or eject oil when the case is under positive pressure). With GMS this left two issues, first is a far excessive fuel consumption, the second was the engine would continue to run even with the throttle barrel completely closed. Even a finger over the top of the carb would not shut down the motor, which indicated how much air must be getting in elsewhere.

In your case there may be other contributing causes. First and easiest to fix is ensuring the prop is balanced. Next is that the drive washer and crank spacing is correct to properly preload the bearings, If off they can wear out pretty quickly, the smaller front bearing usually the first to go. If that bearing allows for radial movement you can wear the case bore and suffer the same mixture problems described.

This is one reason I aim to use good quality bearings. Saving a few coin on less expensive pieces ends up false economy and can take out the rest of the engine as they fail.

So, that brings up perhaps the answer to your question. If the front bearing is wiped you may present end or radial play, excessive oil thrown from behind the drive washer or need to run the mixture so rich you will load up the engine.

What plug are you running? Have you tried one of a hotter range?

ochsnm00

If there is too much blow by the crankcase pressure will be too low to force the fuel mix into the combustion chamber. To test remove the glow plug and turn the engine over smartly. You should hear a woosh from the plug hole. If not there is a crankcase leak ie. back cover, carb base or front crankshaft. It is the front case to crankshaft fit that seals blow-by. A bad bearing should feel rough , when turned, or have play. If a bad bearing has ruined the case it is usually not worth fixing. Check out the diagnosis section on the MECOA site.

aspeed

Sometimes the Fox has a stud for the propeller and the hole is drilled through. This can leak air and can be sealed with RTV. Fuel will normally seep out the front near the bearing if that is where it leaks. Some manufacturers have a groove or hole drilled to stop the seeping oil. This can allow too much air in, which affects idle and low speed running. Not sure about the Fox.

ochsnm00

This article should help. http://www.fayettevillercclub.com/id68.html

carlgrover

The flameout occurs at fast throttle ups. It used to do it only when I shot a touch and go. It's getting worse now and does it on the ground as well. Carb is the twin needle with the flange and two screws to hold it on. It didn't always use to do this years ago. I also should mention this motor has a lot of flights on it. Runs fantastic at full throttle though. I've adjusted both needles and cannot dial this out. I've been running these engines for about 30 years so I am not inexperienced.

I don't think it's a needle taper problem since it ran better years ago. I run nothing but Fox RC long or miracle plugs. I did change the plug recently and it made no difference.


carl

Cougar429

My Feedback: (3)

Sounds like what you are describing is a lean condition at low throttle. Wonder if you are losing draw when the throttle is opened quickly. Stumbling would show rich at idle.

With the time on that engine what is the compression like?

I'm making the assumption nothing physical has changed, such as tank position, etc. One thing you may want to look at would be the fuel lines and tank internals. I had one give me problems on the 50BB since the new clunk line was too soft and would compress above half throttle, starving the engine. Cannot remember the make, but one of their carbs was notorious for rich mid-range. I opted for the adapter and fitted an OS carb in an attempt to cure it.

Have you checked the carb base gasket?

fliteline

Hi Carl,

A few questions, if I may....

Has the engine been in fairly continuous use, or has it been stored for a time and recently put back into service and is now exhibiting this problem?

Will it idle slowly for a reasonable period of time, and if so will it throttle up reliably if done slowly?

Are you using different fuel than you previously used in this engine?

Have you tried an idle bar plug since the engine started doing this?

If you've read this article: http://www.fayettevillercclub.com/id68.html you'll note the tendency for flameouts on throttle transitions depending upon what head button version the engine has, and the nitro content. I'm the author of that article, by the way. Although the engine worked ok, many flights ago, over time there will have been carbon buildup on the top of the piston and the head button which may now be aggravating the situation.

carlgrover

The compression seems to be no less than either my other Fox 50 or my new 45. The carb base has been sealed with high temp silicone sealant. The tank has been out recently and all the lines checked.

carlgrover

This motor has been around for quite a while. I ran it for years then stored it for several more. I put it back into service a few years ago on the current plane and have been running it regularly since. It ran fine for a long time now this problem has been creeping up. It's to the point now that it not only flames out under load (touch and go) but also on the ground. I should mention that when I set the idle on the ground it would be fine then when chopping the throttle for a landing it will be idling much higher than I initially set it. Does that every time. Very aggravating. It will idle on the ground for a good while no problem. I've never tried throttling up real slow. I've started using 5% instead of 10% about a year ago on all my motors. None of my other motors have this problem. Really couldn't tell a difference. I just checked and at the moment I am running a new Fox RC long non idle bar plug. I'd be willing to be there's plenty of carbon buildup on the piston and head. This engine is no spring chicken and has been run for a long time. I have read that article and everything else on your old website. Very good stuff. Wish it was still up although I do have some of the articles copied.

fliteline

Hmm... yeah, high time engine and gradual onset sounds more like a wear problem "somewhere." Just for interest, you could try installing the carb. from your other .50 to eliminate that as a source. Could well be that it has come to the end of its useful life after years of service. Rebuild time - but of course, we know current parts situation.

As for the website info, I still have it all, just in html format. I could convert stuff to pdf for those looking for something specific. I also have all the manuals in pdf format if anyone needs anything in that regard.