Charley

My Feedback: (2)

The HS needle goes on the fixed side where the fuel inlet nipple is located. The LS needle goes into the rotating drum. I think I'd replace the LS needle if I could find one. When I ran Foxes a lot I used to have a handfull of LS needles because the .50 had a way of loading up in the midrange & dying, right at cruise power. I'd swap 'em around until I found one that made the engine run right. I have the .50 manual that I could scan in if you'd like.

CR

1QwkSport2.5r

Earl posted links to a bunch of manuals and Sharon is mailing me the manuals for the other engines.

I know what locations the needles are supposed to be, but common practice of the big tapered needle being the high speed one is incorrect in some of these engines. I will look at my ABC .40 and see if it's setup the same way.

1QwkSport2.5r

This picture sums it up for me. This is a modern Fox .40BBRC ABC. It has a lower compression coned head for higher nitro and a Miracle plug. Otherwise is virtually the same as my Lapped .40 with the weird carb needles. This pic shows the needles from their respective holders; idle on the left and high speed on the right.

1QwkSport2.5r

Fox .50 needles. Low/Left High/Right. Found a spare high speed needle for the .40 too.

Charley

My Feedback: (2)

I just looked at a Fox .50 I had in storage. The LS needle is the tapered one. I thought that needle of yours was awfully blunt but I didn't realize that the needles were swapped in your carb.

CR

1QwkSport2.5r

That was the problem I suspected but didn't think about it until after the fact. Having not seen Fox needles before, I installed them where I expected them to go. Checking my other Fox engines confirmed my suspicion. I haven't found the forum where I read about an engine having reversed needles and related issues yet.

1QwkSport2.5r

Switching the needles gave the opposite results if hoped for. Top end was so rich it wouldn't rev faster than 5,000rpm on top but could adjust a good idle out of it. Put the needles back the way I had them (blunt in the idle and tapered longer needle in the high speed holder) and got 14,140rpm peak on the same 10x5APC and FAI fuel/Fox idle bar plug combo but loaded up horribly at idle even with the idle needle seated. Tried the other blunt needle I had with the same result. It is obviously too rich on whichever end has the blunt needle. Leaving glow heat on does not help. Back to square one.

Charley

My Feedback: (2)

I wonder if that engine ever ran right. Judging from the wear on the knurled parts of both needles, they had plenty of adjusting made to them. With the LS needle where it belongs, you ought to be able to shut off the fuel flow completely by screwing the HS needle in against the stop. If you can't the the HS needle is at fault or the seat in the spray bar is damaged. I'm thinking now that the blunt HS needle is the wrong one or is damaged. Sure hope the spray bar isn't damaged internally by running the needles in from the wrong ends. Have you thought of trying the HS needle out of your other .40?

I'd love to have that engine on my test stand! No offense to your expertise but I love problem solving. BTW, I saw that Fox has the needles available on their web site.

CR

jeffie8696

I hope you figure it out, my buddy is having the same problem.

1QwkSport2.5r

I'm using the complete carb from my single BB .40 (Mk V) because the carb from that came on this engine was missing the barrel and throttle arm and LS needle. I could not get air to stop passing through the fuel line with the carb barely open and the LS needle seated. It's such a minute amount besides, I'm not terribly concerned. However, I can try the other carb and swap in the barrel/arm/LS needle assembly and try it. The engine I'm working on came to me appearing to be run lean and hot. The head button was black and dry as was the top of the piston. So I presume this engine ran closer to optimal than it is now. I'll assemble the other carb and try it. If unsatisfactory results, I'll pull the carb off my ABC .40 and try it out. Something's gotta give.

1QwkSport2.5r

Fixed the problem. See picture below. Spraybar on the right came out of this carb (from a Mk V .40) and the spraybar on the left came from the partial carb from this engine. Put the left spraybar in this carb and installed the blunt needle in the high speed and the tapered needle in the idle holder. Video shows it pretty rich on top yet, idle is a tad lean still. Didn't have but 10 minutes to setup and test run it.

http://youtu.be/NUUAy4xt35Q

Charley

My Feedback: (2)

Yippee! I wuz thinking spraybar, 'member? Now, see if it will run at half throttle for 3 min or so without dead sticking. If it will, you can fly it with confidence.

CR

1QwkSport2.5r

The spraybar was drilled larger, not worn open from the needle. There is a significant difference in jet sizes between the two spraybars too.... Makes me wonder a bit.... This engine cost me nothing, and put an extra high compression head in my parts bin for my ABC .40.

Charley

My Feedback: (2)

Reminds me of my sprint go-cart days. I bought a set of Christensen carbs on a dual manifold for a McCulloch MC-75. But at the track they wouldn't lean out on the top end. Turned out they were drilled out for high-nitro fuel, while straight alcohol was all we could run, or gas. Got my $$ back though.

CR

1QwkSport2.5r

Ran the little lapped .40 for a bit today. I didn't have much time to run it but got it dialed in almost perfect in that time. I had to swap the original high speed needle back in; the end was too long (and narrower) and required being nearly seated to get it into the sweet spot. The old needle had a shorter and thicker tapered end. It idled happily at 2,500 for as long as I let it, but would tick over nicely at 2,100. It throttles pretty nice, though there is a little false needle setting I'm sorting out. Even with tubing on the needle, it still leaks a bit and allows the mixture to change if I bump it causing the rpm to drop (rich). I think the detent clips need to be tweaked and that should help. I'll run more props on it when I get time. It peaked at 13,750 on a 10x5 and FAI fuel today. Pretty consistent in peak revs given the swings in climate lately.

earlwb

That is a early model of the Fox .45 engines. At the time it used a rather small muffler. The two mounting holes are about 2mm more close together than the later engines of which they spaced the muffler mounting holes slightly farther apart. You will have to make a "bridge adapter" to fit a different muffler to it. Or if you are lucky you will find a early style muffler.

To make a bridge adapter, you need one or two pieces of aluminum and you drill it out to fit the engine and the muffler. Then you can effectively use any muffler you want to use.


The early style muffler looks like the one on my old Fox .45 diesel conversion.


Here is a bridge adapter I made for a engine like yours so that a K&B muffler would fit it OK.


A typical one piece bridge adapter, you can offset the holes and machine out the exhaust port at a angle so the muffler will fit.


A typical two piece bridge adapter looks similar to this one, each piece is fitted to the engine and muffler and then bolted together.

Cougar429

My Feedback: (3)

I agree with Earl. You want to fit a standard 40 class muffler such as the OS 873, E-3030, (46LA) up to E-3071, (55AX) as the notoriously loud Fox sound output is cut to the equivalent of the rest of the class with NO reduction in performance.

Here is my 50BB with the same idea. Note I had to use a 2 piece setup due to the bolt spacing between that of the motor and muffler. It would be much easier if the casting used through bolts. Oh well.

1QwkSport2.5r

I use a TT Pro .46 muffler on my standard .40 with a homemade adapter. It needs to be trimmed yet, it's rather ugly (the adapter). Noise is reasonable I think. I have a video posted on the previous page. I've got a Jett muffler that fits too.

Cougar429

My Feedback: (3)

I had posted those numbers as they were the only ones I knew. I've found a lot of the 40 class have identical mounting and port dimensions.

On mine, I spent most of the time filing the ports to match the motor and muffler, which with FOX are considerably different. May not be necessary.

1QwkSport2.5r

I had to offset the muffler aft some because the port on the engine is so small and the muffler so large. I had to spend some time with a dremel to shape the adapter to match both ports. I got it as smooth as I could. It seems to work pretty well. Unfortunately the Fox tilt-down mufflers do not fit my test stand. I guess (for comparison purposes) I could make an adapter to tilt the Fox muffler up, but without having my own lathe or mill it's not feasible. One of these days.....

Hobbsy

My Feedback: (102)

Earl and 1Q, I did similar with this Fox .74 Diesel conversion. I loved the sound of this Bisson Sport muffler. My adapter is not as pretty as yours but works well. Note that the Bisson has two offset baffles, that must be what makes the unique sound. I offset the muffler forward, the rear bolt goes straight into the engine the front has a bolt in the adapter to the engine and another in the muffler to the adapter..The front adapter to engine bolt is countersunk.

1QwkSport2.5r

Fox engines aren't notoriously known for being "pretty" anyway...

Hobbsy

My Feedback: (102)

Yes sir, you have to adopt the, (beauty is in the function) philosophy and at least part of the beauty is in their longevity. I probably spelled philosophy wrong. That is an ABC .74 from the 80 I think. If you flip it slowly you'd better get your finger out of way quickly, it has zero compression leak when flipped slowly.

1QwkSport2.5r

My Fox twin feels like that. The ring seal is absolutely fantastic - It feels like an ABC. Still not broken in all the way yet either. My ABC Foxes are unrun since the factory test run, so they will take some time to run in too. For ABC engines, they're not very pinchy but that doesn't necessarily mean anything.

Hobbsy

My Feedback: (102)

I remember that Dar Zeelon had a fit when I told him that my Fox .74 ABC hd no pinch, he swore that it would never be any good. I think that pinch is way over rated. My LA's don't have much of it either.