Club FOX!
#3651
Ancient history: AMA used to have a once a year coupon special. Fox would list one or two engines as a coupon special with a discount. This caused me to buy several Fox engines that my local hobby shop didn't carry. After trying them, I liked them. Especially a .36 with a carburetor that looked like it was closed when it was open. Seems like the low speed adjustment was the fuel nipple, but the carb worked well for me.
#3652
I have a couple of questions:
I have had my Fox 74 for some time now and got it to work properly in the past. This past weekend I tried it on a different plane that has had other engines flying it with no problems. With the Fox 74, I could tune the top rpms to over 11K with an MVVS muffler (similar performance to Fox stock mff.), 12x6 XOAR prop, and 5% nitro fuel (17% synth, 3% castor). However, when I tilted the plane upwards to check for lean runs, it would lean out easily. So, I ended up having to richen the HSN 2000 rpms lower. With that rich setting, the engine was too weak to power the plane and max rpms were a mere 9300 only. Can anybody suggest any ideas where to look? The engine would still run hot even with 5% nitro, 2 head shims, new head button, and 12x6 prop. It just seems the engine doesn't have enough fuel suction/pressurization and it is still sensitive to heating. Compression, bearings, idle, and throttle response are good, only the top end is weak.
Secondly, I ended up swapping planes with somebody and the plane I got has a Fox 45. Does the 45 require low nitro like the 74? Anything I should watch out for? Compression and bearings seem good, but no muffler.
I have had my Fox 74 for some time now and got it to work properly in the past. This past weekend I tried it on a different plane that has had other engines flying it with no problems. With the Fox 74, I could tune the top rpms to over 11K with an MVVS muffler (similar performance to Fox stock mff.), 12x6 XOAR prop, and 5% nitro fuel (17% synth, 3% castor). However, when I tilted the plane upwards to check for lean runs, it would lean out easily. So, I ended up having to richen the HSN 2000 rpms lower. With that rich setting, the engine was too weak to power the plane and max rpms were a mere 9300 only. Can anybody suggest any ideas where to look? The engine would still run hot even with 5% nitro, 2 head shims, new head button, and 12x6 prop. It just seems the engine doesn't have enough fuel suction/pressurization and it is still sensitive to heating. Compression, bearings, idle, and throttle response are good, only the top end is weak.
Secondly, I ended up swapping planes with somebody and the plane I got has a Fox 45. Does the 45 require low nitro like the 74? Anything I should watch out for? Compression and bearings seem good, but no muffler.
#3653
Senior Member
My Feedback: (3)
What MVVS muffler and does it have a pressure fitting? How old are the fuel system components
What engine was on there before? Asking as carb height or distance to throttle centerline from the tank may have increased.
Only time I encountered something similar I had pulled the 50BB powered Seamaster from 20 year storage. Figured I should change the fuel lines so went with a very flexible clunk line in the tank. Engine fired up and would fly at 1/2 throttle or below all day. Anything above that and it would starve. After tinkering forever and even installing an OS55AX the problem persisted. Found at higher throttle settings the clunk line would actually collapse under muffler pressure.
What engine was on there before? Asking as carb height or distance to throttle centerline from the tank may have increased.
Only time I encountered something similar I had pulled the 50BB powered Seamaster from 20 year storage. Figured I should change the fuel lines so went with a very flexible clunk line in the tank. Engine fired up and would fly at 1/2 throttle or below all day. Anything above that and it would starve. After tinkering forever and even installing an OS55AX the problem persisted. Found at higher throttle settings the clunk line would actually collapse under muffler pressure.
#3654
What MVVS muffler and does it have a pressure fitting? How old are the fuel system components
What engine was on there before? Asking as carb height or distance to throttle centerline from the tank may have increased.
Only time I encountered something similar I had pulled the 50BB powered Seamaster from 20 year storage. Figured I should change the fuel lines so went with a very flexible clunk line in the tank. Engine fired up and would fly at 1/2 throttle or below all day. Anything above that and it would starve. After tinkering forever and even installing an OS55AX the problem persisted. Found at higher throttle settings the clunk line would actually collapse under muffler pressure.
What engine was on there before? Asking as carb height or distance to throttle centerline from the tank may have increased.
Only time I encountered something similar I had pulled the 50BB powered Seamaster from 20 year storage. Figured I should change the fuel lines so went with a very flexible clunk line in the tank. Engine fired up and would fly at 1/2 throttle or below all day. Anything above that and it would starve. After tinkering forever and even installing an OS55AX the problem persisted. Found at higher throttle settings the clunk line would actually collapse under muffler pressure.
The original engine was an OS 55AX until it died. So, I temporarily installed an OS 70 Surpass II, then a Thunder Tiger 75FS, and finally the Fox 74. The engines were mounted sideways, so the carb height to tank is the same. The distance from the carb is greater with the Fox, even though the tubing length stayed the same.
#3656
The reason I did not suspect any fuel plumbing is because the engine idled and transitioned perfectly. It even ran WOT perfectly until tipping up the plane vertically.
Last edited by hsukaria; 09-29-2014 at 12:41 PM.
#3657
Senior Member
My Feedback: (3)
Still primarily suspect a pressure problem or you have a restriction in the carb line.
One thing to remember is that the Fox 74 will require a lot more fuel at full throttle than any of the previously mentioned motors.
What happened with the 55AX, (cannot add question marks till I figure out what format changed on the keyboard. All I get is É).
One thing to remember is that the Fox 74 will require a lot more fuel at full throttle than any of the previously mentioned motors.
What happened with the 55AX, (cannot add question marks till I figure out what format changed on the keyboard. All I get is É).
#3658
Still primarily suspect a pressure problem or you have a restriction in the carb line.
One thing to remember is that the Fox 74 will require a lot more fuel at full throttle than any of the previously mentioned motors.
What happened with the 55AX, (cannot add question marks till I figure out what format changed on the keyboard. All I get is É).
One thing to remember is that the Fox 74 will require a lot more fuel at full throttle than any of the previously mentioned motors.
What happened with the 55AX, (cannot add question marks till I figure out what format changed on the keyboard. All I get is É).
BTW, I just checked that the Fox 74 muffler pressure nipple was not clogged. Maybe the other engines have better fuel suction/pressurization? This problem did not exist before on the Fox 74 in another plane. So, it must be the fuel tank/tubing.
#3660
By the way, here is the engine I acquired through a plane trade, I am told it is a fox 45, but there are no markings on it except FOX. I temporarily installed the EZ carb while I wait for the MKx carb that it came with. I have not run it yet, maybe next weekend.
#3661
If it's ringed, it's likely a .45. The .46's were ABC, the .50's were all ringed but stamped I believe. Has an EZ carb I think. The .45 and .50 liners have punched ports, not machined. The bore of the .50 is .906".
#3662
The previous owner said it came with the MKx carb, but he is fixing it right now. I put in my spare EZ carb for now. I hope to bench test it this weekend without muffler. What is a good prop to start with? 10x6 or 11x6? I also have a 12x4 and 10x8.
Last edited by hsukaria; 09-30-2014 at 07:03 AM.
#3663
I'd think a 10x6 or 11x6 would be good props to start with. If it were me, I'd pull the head off to look at the combustion chamber shape and measure the head clearance to get an idea of what fuel it's setup to run. That's just me being analytical though. I understand running it beforehand to see what it does as not being a bad thing to do either.
#3664
I'd think a 10x6 or 11x6 would be good props to start with. If it were me, I'd pull the head off to look at the combustion chamber shape and measure the head clearance to get an idea of what fuel it's setup to run. That's just me being analytical though. I understand running it beforehand to see what it does as not being a bad thing to do either.
#3665
#3666
Still primarily suspect a pressure problem or you have a restriction in the carb line.
One thing to remember is that the Fox 74 will require a lot more fuel at full throttle than any of the previously mentioned motors.
What happened with the 55AX, (cannot add question marks till I figure out what format changed on the keyboard. All I get is É).
One thing to remember is that the Fox 74 will require a lot more fuel at full throttle than any of the previously mentioned motors.
What happened with the 55AX, (cannot add question marks till I figure out what format changed on the keyboard. All I get is É).
I did re-run the 74 on the bench with a stock MVVS muffler, which is similar in performance to the Fox stock muffler. The engine maxed at 11000 rpms with 5% or 0% nitro fuel. I was only running a 12x6 prop though. Despite that, it felt quite hot after a short run with relatively cool ambient temps (in the upper 40's) and I was using a cooler OS #8 plug instead of the previous Miracle plug. But, I examined the fuel tank on the plane and it had the plastic tubing instead of aluminum or brass. The plastic tubing has a considerably smaller inner diameter, so that might explain the leaning out when holding the plane upwards. I replaced the tank tubing with brass tubes with big inner diameters.
Last edited by hsukaria; 10-08-2014 at 06:29 PM.
#3667
I was not able to get the 45 that I got in a plane swap to start a few days ago, but I was running with a carb that sat for 3 years out of use and I did not have a muffler. I found an old OS muffler in my vast collection of mufflers and am in the process of carving out an adapter for it. However, I kept thinking that the engine felt quite heavy for its size. That is especially since Fox engines typically tend to be lightweight for their displacement. Then I realized why. The engine backplate is filled with what looks like melted lead. Maybe a previous owner needed weight on the nose of the plane? How do I get that stuff out?
#3668
Senior Member
My Feedback: (3)
If the engine runs full throttle in a standard attitude and then leans when held nose up I still suspect you have a feed issue, one that hints at inadequate muffler pressure or a deficiency in the carb to draw fuel under the higher demands created when the tank is dropped a considerable distance below the carb inlet.
Not sure about the plastic tubing being at fault as any flow restrictions would be present regardless of attitude, (meaning a condition where the lines cannot flow enough to meet demands would be evident at all times)
I've been running plastic tubing for nearly 2 decades now, all the way up to a Saito 150 with no problems. If checked against the aluminum tubes supplied with some ARF setups the ID is pretty close to identical.
Also would be leery of warming up the rear cover enough to flow out the lead as that temp may be close to the melting point of the alloy, as well. May require a bit of drilling around the periphery close to the cover and then trying to pry out the inner chunk. Any remaining lead may then come away with a bit more work.
Sorry, very tired and may not be explaining things clearly.
Not sure about the plastic tubing being at fault as any flow restrictions would be present regardless of attitude, (meaning a condition where the lines cannot flow enough to meet demands would be evident at all times)
I've been running plastic tubing for nearly 2 decades now, all the way up to a Saito 150 with no problems. If checked against the aluminum tubes supplied with some ARF setups the ID is pretty close to identical.
Also would be leery of warming up the rear cover enough to flow out the lead as that temp may be close to the melting point of the alloy, as well. May require a bit of drilling around the periphery close to the cover and then trying to pry out the inner chunk. Any remaining lead may then come away with a bit more work.
Sorry, very tired and may not be explaining things clearly.
#3669
Banned
Thinking what I would try
I can tell you what I would try.
I would not use any heat.
I would remove the back cover ( 4 screws ).
I would use soft jaws in a vise or some semi-hard wood like pine to hold the back cover in the vise
I would tighten the vise just enough to hold the back cover solidly.
I would use a small 'cold chisel' about 1/4" or 3/8" wide and a small hammer and start chiseling away in a direction 90 degrees to the vise jaws.starting at the outer edge of the lead and hammering toward the center.Some patience would be needed removing a bit at a time.
An alternative to a small chisel could be a screwdriver that has been ground on one face only to make the equivalent of a wood chisel in shape.
I would want to avod hammering the periphery of the back cover which I assume is aluminum.
I do not know your tooling facilities but another way would be to use a small drill press and a 1/4" dia ' end mill '. Adjusting the lowest reach of the drill just to avoid touching the back cover.
Wishing you success in removing that material.
Zor
Last edited by Zor; 10-08-2014 at 09:08 PM.
#3671
Lead melts at what... 500-600F and aluminum melts well above 1,600F. The lead had to be heated to get it in there. Heat it to get it out. Cookie sheet with some foil, and broil it! If the back cover warps, oh well.
#3672
If the engine runs full throttle in a standard attitude and then leans when held nose up I still suspect you have a feed issue, one that hints at inadequate muffler pressure or a deficiency in the carb to draw fuel under the higher demands created when the tank is dropped a considerable distance below the carb inlet.
Not sure about the plastic tubing being at fault as any flow restrictions would be present regardless of attitude, (meaning a condition where the lines cannot flow enough to meet demands would be evident at all times)
I've been running plastic tubing for nearly 2 decades now, all the way up to a Saito 150 with no problems. If checked against the aluminum tubes supplied with some ARF setups the ID is pretty close to identical.
Also would be leery of warming up the rear cover enough to flow out the lead as that temp may be close to the melting point of the alloy, as well. May require a bit of drilling around the periphery close to the cover and then trying to pry out the inner chunk. Any remaining lead may then come away with a bit more work.
Sorry, very tired and may not be explaining things clearly.
Not sure about the plastic tubing being at fault as any flow restrictions would be present regardless of attitude, (meaning a condition where the lines cannot flow enough to meet demands would be evident at all times)
I've been running plastic tubing for nearly 2 decades now, all the way up to a Saito 150 with no problems. If checked against the aluminum tubes supplied with some ARF setups the ID is pretty close to identical.
Also would be leery of warming up the rear cover enough to flow out the lead as that temp may be close to the melting point of the alloy, as well. May require a bit of drilling around the periphery close to the cover and then trying to pry out the inner chunk. Any remaining lead may then come away with a bit more work.
Sorry, very tired and may not be explaining things clearly.
Thery is no problem with the lead melting, lead melts at 621 degrees F and your engine would be ruined at a much lower themperature.
#3673
If the engine runs full throttle in a standard attitude and then leans when held nose up I still suspect you have a feed issue, one that hints at inadequate muffler pressure or a deficiency in the carb to draw fuel under the higher demands created when the tank is dropped a considerable distance below the carb inlet.
Not sure about the plastic tubing being at fault as any flow restrictions would be present regardless of attitude, (meaning a condition where the lines cannot flow enough to meet demands would be evident at all times)
I've been running plastic tubing for nearly 2 decades now, all the way up to a Saito 150 with no problems. If checked against the aluminum tubes supplied with some ARF setups the ID is pretty close to identical.
Also would be leery of warming up the rear cover enough to flow out the lead as that temp may be close to the melting point of the alloy, as well. May require a bit of drilling around the periphery close to the cover and then trying to pry out the inner chunk. Any remaining lead may then come away with a bit more work.
Sorry, very tired and may not be explaining things clearly.
Not sure about the plastic tubing being at fault as any flow restrictions would be present regardless of attitude, (meaning a condition where the lines cannot flow enough to meet demands would be evident at all times)
I've been running plastic tubing for nearly 2 decades now, all the way up to a Saito 150 with no problems. If checked against the aluminum tubes supplied with some ARF setups the ID is pretty close to identical.
Also would be leery of warming up the rear cover enough to flow out the lead as that temp may be close to the melting point of the alloy, as well. May require a bit of drilling around the periphery close to the cover and then trying to pry out the inner chunk. Any remaining lead may then come away with a bit more work.
Sorry, very tired and may not be explaining things clearly.
Regarding the lead in the backplate, I just wonder why all this crazy stuff happens to me. Why me, why? (actually, I am seeing this as a learning challenge, but just had to add a little melodrama).
#3674
It also seems that there is some glue around the seam. I might be lucky and get that glue to crack and drop the lead out without having to melt it completely.
#3675
Banned
More thinking worth trying
Your post made me look at the pictures again.
It does not appear as if the lead ( could be tin or a soldering alloy ) has been melted upon the back cover. It does not reach the flange all around and its surface is not smooth.
Suspicions are that it was formed away from the back cover and can very well have been cemented.
Still with the back cover removed from the engine it may be worth trying some low heat from a hair dryer or a heat gun being carefull to heat it up slowly and watch what is happening.
When there is a will there is a way ... L O L
Zor