Ok, I went out today and tried the old Fox 40 I found with the oldest throttled Carb Fox ever made.

I started the needle values at 3 turns out and the fuel overflowed out of the carb. I turned the high speed needle value to 2 turns and the low speed to 1.5 turns (that seems to be where the fuel was guzzling in mostly) but it took me 20 minutes to "dry" the engine out with the fuel disconnected.

But, I got it running!! Leaned out the low end adjustment to about 1 turn out. The high speed to about 1.5 turns out. It ran ok. Power was so-so but nothing to write home about. I think about average for a bushing 40. It seemed to be turning nice RPM's though...probably around 12,000 with a 10x8...so a 10x6 or 10x7 would probably get it on up to 13. Basically, the needle adjustments on this carb are extremelly rough. The low speed needle practically turns on its own. I used a big screwdriver and I didn't have any problem with getting burned or "cut" since its about 1/4 inch away from the prop. The low speed needle has a wide setting where it does little and either side of that it stops the engine. Also, the low speed setting has a much more dramatic effect to the high end that I've seen typically.

The negatives are this. If I set the engine to idle it seems to idle fine, but if I open the throttle quickly it has a tendency to "drown" in fuel. I can see the fuel literally bouncing around inside and out the carb throat after rushing the throttle. But, finally the engine will start catching up and the fuel girgling in the carb will stop and the engine will start to suck the excess fuel in the carb down and increase and hum -- but its a good 5-10 seconds for this process. Adjusting the low end setting doesn't seem to have a huge effect on this. I eventually leaned to just less than 1 turn and it still did this. Its like the engines carb has no effective way of dealing with needling fuel in the middle range. Also I noticed the engine has to be set quite "rich" on the high end because as the motor heats up it continually leans out more and more. If you set it too lean, it will heat up, overlean and stop. I think the engine is still so new that it has to run rich still for a little longer and this will probably more than likely stop.

This engine is probably way too "unreliable" for a $250 balsa model because of the old carb. I was planning on putting it in a spad where an ocassional flame-out would just provide an enjoyable challenge.

It was fun getting the old guy to run though...gives you confidence that you could get any engine running.

Pictures

[link=http://www.comcity.com/rc/images/fox40-5.jpg][/link]
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[link=http://www.comcity.com/rc/images/fox40-2.jpg][/link]

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Ohhhh..one of these! By all accounts they're supposed to be quite powerful and I think they're called a "barn door" Fox because of that rather unique backplate. They come in both 40 and 45 size with the size being stamped on the left mount lug.

Really??? BarnDoor. So it is suppose to be powerful compared to what? Maybe its an ok engine then...??

Yep just 40 stamped on the mount...nothing else...not even the words FOX. And, the 40 stamp looks like someone did it with a metal stamp and hammer...nothing fancy at all.

I think I still have one of those but mine is almost black af all the casteroil burned into the metal, but still good for a 40 size plane..
if you would like to put her on a spad, try it on a McDDD ( almost a spad3d ) , or a QHor and 11x4 prop, and a mouse can pipe, you hover the the plane just fine. I have seen these hover with TT42GP and a 11x4 with a standerd silencer.

A old motor that has run a lot is better than one that has run once and was stored for a long time, you might need the replace all the seals under the card and make sure there is no air leak in/under the card, or just get a new card , much cheaper than a new motor..

Sounds like you need a hotter plug. Fox actually recommends the Miricle plug on some of their engines. Have you tried the Flightlines solution site. Pretty sure there is a operation manual on the site. I have a Fox .50 and though the serrations on the needle are course, they don't need to be finer. Needles are not sensitive at all. What nitro are you using? May make the needle less sensitive by stepping up the nitro.

PS: Fox still has parts for this engine. In fact they still sell it, with a differant carb.

I'm running PowerMaster 15% (18%) I added some more Castor by hand to bring it closer to 20%. Not for this engine...its for by 4 cycles that like a little extra Castor.

I thought the fuel too...but everything I've read says use 5% or less. That Fox engines don't like a lot of Nitro. I was thinking about cutting some of the 15% down or seeing if I could find something less.

Also a biggee. The muffler I "modified" for the engine is tapped, so I hooked it up for tank pressurizer. I'm starting to think that this could be the problem. I know for a fact that muffler back then especially for the FOX, did not have this feature. When this engine was purchased....mufflers was just starting to get used. Many engines ran without mufflers altogether. Another thing I've read about Fox's, their carbs were designed to be able to suck the fuel out of the tank "without" the need for extra pressure. This manifold pressure might be forcing fuel into the carb. Running it ---that sure looks to me like what was happening. It was like someone was blowing "extra" fuel into the carb and the engine was busy sucking as much as it could but had to catch up.

I don't know what kind of glow plug....it was on there. I heard it sizzle, I felt it thumb when I turned the prop so I went with it. It looks like a Fox. I still mainly use Fox glow plugs. I'm surprised you would need a miracle plug though...I have some. I'll try.

Don't get me wrong, the engine ran pretty good. It continued to run through the transition of throttle increase just seemed to hesitate on the fuel uptake. Didn't instantly increase RPM's but went through a 7 second transition or so.

Yes, new carbs are $33. I could get a Perry Carb as well for about that much...which is probably the way I would go if it made sense. But a new 46 is about $70. $33-$35 is half way to a bigger, newer, more powerful engine. A new carb just makes no financial sense. I think I would E-bay-it first.

Yes, thanks Sport_Pilot. Are you kidding me? I wouldn't have gotten the engine to run at all without their help. I give them guys [sm=thumbup.gif][sm=thumbup.gif][sm=thumbup.gif] (3) thumbs up.

The folks there as well as Fox told me that this carb is a bit finiky -- don't expect too much. lol

Looking at your picture a little closer the carb is a very early Fox carb. I think it may be older than the engine. The back door 40 came out in the late 70's or maybe the early 80's. That carb looks like the ones they made in the 60's through mid 70's. My .50 has a MKX carb, and though it looks crude by todays standards it actually works pretty good. This may be a case of someone replacing a broken carb with an older one on hand. If so then it may be a problem of a mis match. I had a Fox Eagle .60 I bought without a carb, couldn't get it to run right with a Perry 60 sized carb I had on hand, bought a used Fox carb and it ran great! Don't think it was the carbs fault, just a mismatch of some sort.

No, this engine is circa 1974 and this type of carb was all there was...no other version existed except for the control line versions. I'm the original purchaser and thats the carb that came with the engine. Purchased it from Hobby Shack as I remember.

All of that was confirmed by Flightline and Fox including the fact that this carb is very hard to work. Also Flightline said if I changed out the carb and put in a Perry or even a new Fox carb....I would believe that I just purchased a new engine. But since I really need a 46 anyways, it isn't worth doing that.

But since I really need a 46 anyways, it isn't worth doing that. I don't know, Fox's are fairly high performance engines. The numbers you posted are fairly impressive and it isn't even broken in yet. It won't have the performance of a .46 but with a good carb should be a good performer. I would think the present Fox muffler would fit, if not then Tatone and others make strap on's, and Mac's Mufflers probably has a manifold for it. I would buy a carb and use it on a spad or something. BTW did you use 100% castor oil?

Also maybe I have bad memory but I thought the Barn door Fox's came out later than that. Check out E-Bay, you can buy junker Fox's with good carbs for a lot less than a new carb. Look for the MKX twin needle.

Yes, I think it would be an ok 40. Better than the LA...comparable to the FX from OS.

Since I really need a .46...I need to kick @#$!% lol. I want to build a spad3d. The present day FOX mufflers are different. Tried on at the hobby store. They moved the mufflers holes out about 1/4 inch or so. The muffler I modified is a MVVS and it fits good just a tiny bit small but I don't see it causing problems if its not overpressurizing. I would probably cut it open though and add a mousse can to it anyways in the end.

I took 15% powermaster and beefed up the castrol by about 4-5%. I don't think that powermaster is 100% castrol. The engine was not that hot when it ran out of fuel....I could touch it and hold on to it no problem in less than 30 seconds. Nothing like todays engines.

I don't know what the name of this engine is....? I do know I graduated HS in 1980 so that was at least several years after I bought this engine. Maybe they were just putting these crummy carbs on at first and then changed shortly after.

The parts carb is a good idea...thanks.

Oh gosh...heres one on Ebay with the exact same carb. This thing is not even worth auctioning at $11.50

[link=http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3152658181&category=34 055#ebayphotohosting]Same one[/link]

It seems Fox still make engines with that unusual backplate as I found out from http://www.foxmanufacturing.com/products.htm but the major change from your engine is that the boost port channel has been revised (going by the photos of the latest engines).

There's a short thread (with photos) on the earlier engines at http://www.clstunt.com/cgi-bin/dcfor...rum=DCForumID1 and there's mention of the piston skirt being longer on the exhaust side. Going by the photos of the boost port channel on your engine and the other earlier one this indicates that it had a true boost port that's sealed off from the crankcase by the piston instead of being directly connected to the carnkcase like all other common Schneurle engines are. That's just a guess but it'd be interesting to take off that backplate and have a look

I don't enough about engine mechanics to know what your saying...lol

But, the CL engine in that picture is "EXACTLY" what I have but with a throttled carb instead of an open ventura.

Oh, wait, now I know what your talking about....I did take this engine apart once to clean it and yes, the piston has a longer side on the exhaust side

Note on that link downunder sent that one post said that this engine likes nitro. It is only the present .60 and .74 engine that likes low nitro. The rest like mid to high nitro.