1QwkSport2.5r

Anything that needs to be done to the .46 ABC? I have one NIB. I'd probably put a diesel head on it if I can find one.

I also have a .50BB with a fitting diesel head, but the .50 I have is a piece of junk. If I had access to good new parts, I'd keep it in service as a diesel. Instead I'll put the MDS .40 piston/liner back into my .50 case and make it a running .42 displacement ABC Fox.

I also have a C-case .40 ABC that was new. It came with a high nitro head button and I have a low nitro button as well. It runs okay, but the liner is out of round. Piston seal isn't great, some chrome is ground off around some of the ports inside the liner. I'll punish this one on diesel.. The beat up lapped .40 I have (Mk. V; 1983) runs decent as a diesel except it won't idle. Piston is gouged from a broken circlip some time ago.

Ive had other Fox engines, but I've not been all that happy with any of them. I don't have high hopes for the .46.

Hobbsy

My Feedback: (102)

Tim run that .46 about 10 minutes to set the needles set and go fly it for the rest of your life, it won't wear out. I think this ones a .46.

1QwkSport2.5r

The .46 seems better made than most of the other Foxes I've had in my hands. It has a nitro friendly head in it. I had it for sale for quite awhile. I might have the diesel head for the .50 cut so it fits the .46. I gave up on the .50 indefinitely. I tried the piston/ring/liner I got from you in it on glow and it struggled to turn 11,000rpm on a 10x6. Tried a new Bowman ring and it got worse. I have so many engines in this displacement that are far more powerful and reliable that I'd use those first anyway. It's too bad I missed the "golden age" of glow engines.

I have an Irvine .46 now that was given to me. Needs some stripped head screws re-tapped first. Has a Jetstream carb on it.

hsukaria

The Irvines with the Jetstream carb are fantastic engines. I have a couple of older 40s that I will start using again soon.

hsukaria

While we are on the subject of Fox engines..I recently had a muffler bolt break in my engine and it broke in deep under the surface. Do you guys have a good way to remove it? I can't seem to find a small enough extraction kit in my local hardware store.

1QwkSport2.5r

Try a left hand twist drill. I tried this on a broken bolt in the cylinder head of a Chevy 350 and it worked great. A model engine is smaller obviously, but a LH drill may do the trick. Just use a smaller bit than the hole and try to center it as good as you can.

hsukaria

I guessed that is what I need, but I have not found a small enough left hand drill bit. I will keep looking.

RichardGee

My Feedback: (156)

I used to fly Fox engines (20 years ago). The .46 ABC with their short tuned/pipe muffler was the best running Fox I ever owned... which is to say, it performed about like a Super Tiger of similar displacement. I dieselized a Fox .74 and installed a Fox .40 sized carburetor on it for this purpose. I thought I had come up with a really great combo, as occasionally it impressed me with its idle, throttling and good top end torque. But it also tended to overheat and run over-compressed just on its own. I could NEVER fly the thing for fear this would happen in the air where I had no access to the compression screw. I finally gave up on it (and all my diesel doings) and switched to GAS. Never looked back.
Sad to see that Fox no longer produces engines. They could have lasted much longer if they had modernized, but ultimately, glow's best days are behind us.

carlgrover

From the questions above about my engine problems and (looking for a solution) I got curious about whether or not my Fox .50 would idle for a long time so I took it out to the flying field today. When I let it idle it would hold the initial rpm for about 15 seconds or so then it would drop. After the RPM dropped it would idle maybe another 20 seconds then quit suddenly. I adjusted the low needle a few clicks rich and tried again. Same result. I kept adjusting rich, checking the idle, it would die, then repeat. I did this until the needle was nearly out and the engine didn't really behave any differently. I noticed quite a bit of fuel running out around the OD of the carb barrel. It will keep running if I slowly open the carb but it stumbles about mid range. Fast acceleration will kill it every time. I tried idling it with the glow ignitor on thinking maybe my plug was bad but it behaved the same way. I also flipped the prop over hard without the plug in it at all and there wasn't much "whoosh" there. Lastly, I pulled on the prop in several directions and didn't notice any movement of the crank.

I think the main problem is the leakage around the carb barrel. I also think the engine is pretty much wore out.


Carl

Hobbsy

My Feedback: (102)

The slowing, then slowing again indicates a too rich condition, not a lean condition, leaning the LS needle would most likely make it idle forever.

spaceworm

I suggest you check the glass plug seal. I had several Fox idle bar plugs leak at the glass seal, and cause running issues. I wrote to Fox and was basically blown off. It seemed they just did not care even to get the bad plugs back for examination. I do however use the Miracle plugs in my 4S Saito and YS engines to good effect.

Sincerely, Richard
AMA 861960
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
YS F 120;

hsukaria

I had similar problems a couple of years ago with a bad batch of Fox glowplugs. But the Miracle plugs are good.

Charley

My Feedback: (2)

Carl,

It sounds to me like it has a bit of an air leak after it comes up to operating temperature. A little hi-temp RTV on the backplate and a check of the tightness of all screws is in order, IMHO. Wouldn't hurt to pull the head & scrape the carbon out either. I'd go back to 10% fuel with some castor in it too.

CR

carlgrover

I've already ran high temp RTV everywhere there is a seam. All around the carb base, the backplate, muffler, everywhere. All screws are tight.

I haven't scraped the carbon off the piston though. I'm more worried about all the excess fuel dripping out of the carb barrel.


carl

blw

My Feedback: (3)

If you have a mystery air leak have you changed all of the fuel tubing and brass tubing? All of it? RNV to carb if you have it? Gas tank innards and the brass tubing? It cracks inside the stopper sometimes. The vent line from the muffler can soften on the inside and collapse once you warm up the engine in the air. Fuel tubing does the same thing in fuel jugs too and pumping will cause the tubing to collapse and close off.

1QwkSport2.5r

I suspect a poorly sealing ring or worn liner as being the culprit possibly. If there isn't a good pop from turning the engine over quickly sans glow plug, that alone may be the problem. Being able to run the needle so rich it's almost falling out doesn't change the tune of the engine (much) tells me something is seriously amiss. Poor crankcase pumping would cause this as well as a gross leak elsewhere. I don't think the carburetor to be the major fault here. The idle and transition is the first to suffer when piston seal goes to crap. Without having the engine in hand is tough to surely diagnose though.

carlgrover

I think I'm going to consider this engine worn out and leave it at that. It has hundreds of flights on it so I'll just keep it for parts.

Maybe Fox will start making engines again and I can trade it in on a new .45. I bought one just before they shut down and it really is nice.


carl

aspeed

Before you toss it, you could do the old Fox fix. More oil. Solves wear problems, and repairs them too.

hsukaria

Thick castor oil that is...

carlgrover

I've been adding 3 - 3 1/2 oz of castor oil to a gallon of fuel which contains about 18% oil for many many years already.


carl

1QwkSport2.5r

The synthetic oil in most fuel is much lower viscosity than castor and that thicker oil is what you would need. You would need to bump your oil up to 25% or higher to see any improvement if there is any improvement to be had. FWIW Fox fuel was all castor which is what all Fox engines were run on at the factory.

Sport_Pilot

Some of their engines must use all castor. Mostly their iron piston in iron sleeve engines. I have a Fox .50 and it runs just fine on Omega 5% fuel. It will tolerate 10% on a cool day, but it really likes 0% nitro. That might be some of the OP problems.

Hobbsy

My Feedback: (102)

Tim, that statement does not apply to Wildcat full synthetic, the Wildcat lube is thick and lays on my test stand board nearly an eighth inch thick and does not run off the board fast when I stand it on end.

You can see it laying thick behind this Saito 1.15, the black streaks are from a black grease that was on the rod ends from the factory.

1QwkSport2.5r

That's why I said most fuel. Though the cold viscosity is often much thicker than when it's warm like when it's pumping through the engine. How the oil behaves warm is more important than cold IMO. In the case of the fellow with the misbehaving Fox .50, the castor varnish would likely help the ring seal better. The trouble (I use this term loosely) with synthetic oils is they remove the varnish (or in many cases never allows it to form) which will mean a worn ring could leak more. Perhaps a few tanks of varnish fuel (all castor lube) may help the ring seal better and possibly make the engine run better. I'm sure a lot of guys know I'm more of a proponent of castor, but don't get me wrong... Both castor and synthetic oil have their places (and their good and bad qualities). IMO - Fox engines were designed when castor was "King" and because of that, I for one would not run one on anything but castor laden fuel regardless of cylinder construction in a Fox. Just my two cents. Not saying everyone should follow my regimen, not everyone likes to experiment like I do. I'm actually in the process of running in a Picco .28 RC car engine in one of my RC trucks. I'm messing with fuel mixes to get the best results even though the manual states to use 10% castor oil. These engines tend to run a little cooler with synthetic oil, but they seal better with some castor in the mix.

aspeed

I really hate to get into a castor oil discussion as they can get quite heated. When I flew F2A Speed, as it is now, it mandates castor and methanol with no nitro. They needed to be cleaned of varnish every 20 flights or so because they would slow down noticeably. They were both steel piston and ABC at the time. The TDs .049s were the same. Foxes seem to need it for a varnish plating. I have a few old worn Foxes with very loose bearings. They need thick oil to seal, the piston cyl. seal seems fine though.