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Thread: ma3spa carb

  1. #1

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    ma3spa carb

    does anybody know of an online rebuild manual or diagram for the ma 3spa

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    S2D's Avatar
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    I may be wrong but that probably won't stop me from arguing about it.

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    I have pulled my carb apart and i have found that the jet is free and clear. the mixture shaft seems to be unworn and the carb in general looks fresh and new with one exception. the inside of the carb has soot. there is soot around the jet inside and out. there is soot inside the bowl. the soot looks like black carbon from maybe a fire although no signs of heat.



    this gets me to my problem i have mo mixture control other than on / off as i slowly pull the mixture back the engines will suddenly hesitate then die if i continue to pull back.

    the engine is a c85 any help would be great

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    cubdriver2's Avatar
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    Quote Originally Posted by swoeric View Post
    this gets me to my problem i have mo mixture control other than on / off as i slowly pull the mixture back the engines will suddenly hesitate then die if i continue to pull back.

    the engine is a c85 any help would be great
    Isn't that what it's supposed to do?

    Glenn

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by swoeric View Post
    this gets me to my problem i have mo mixture control other than on / off as i slowly pull the mixture back the engines will suddenly hesitate then die if i continue to pull back.

    the engine is a c85 any help would be great
    intake leak allowing more air in from other places???

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    It's kind of hard to understand your problem.

    It sounds like :

    During operation as the Mixture is leaned it drops off instantly.

    Normally a correct mixture will have a slight rise before it shuts off.

    Have you checked ( & how) did you check Idle Mixture?

    As Mike said; a leak in the Induction System will cause Lean Operation.

    A Lean Mixture drops right off.

  7. #7
    Hardtailjohn's Avatar
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    The "soot" that you're seeing is most likely a hose coming apart on the inside. Had that alot, especially if mogas has been used. I look for about a 50 rpm rise just before the engine dies at idle, when the mixture is eased back very slowly.
    JH

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    the engine does drop off instantly from all rpms and temps. i was able to pull it back some with no effect on a -20 day.

    I am unable to lean to achieve a max power or rpm rise.

    I have been all over the intake and there are not any leaks. I had one before and it caused a bit of popping. This has been remedied. The primer is located in the #1,2 cylinder heads. the spider is completely blocked off.


    The only thing I havent checked would be what my actual jet size is and or should be. In theory I would be safe a bit fat because i could manually lean it out..(I plan on Crank and Pistons soon ).

    What is the quickest way for me to find the jet size for a c85, 90, 0200, and 0235 ... good chance they are all the same?

  9. #9
    Cub Builder's Avatar
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    This sure sounds like a familiar problem. Check those things already previously listed, but also check the part number on your carb against the part number specified for your C-85. Make sure you have the correct venturi and jet for a C-85. If one is running a MA3SPA intended for a larger engine, the jet and venturi are likely the wrong size. That makes the mixture control extremely touchy, which is exactly what you are describing. I saw this problem one other time when a friend tried running a MS3SPA off from a 150 Franklin on his C-90. The symptoms were very much as you describe. I know the carb he was using was good as it came off from my Stinson. The solution was to get a MA3SPA with the correct part number for his C-90.

  10. #10
    www.SkupTech.com mike mcs repair's Avatar
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    is this a NEW problem??? or has it always been like this since you have had this plane???

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    since ive had the plane. On the tcrafters site most of them had strombergs without a true mixture control or it was wired off.. i was under the assumption this is what i had and never gave it a second thought...then while chasing an intake leak (bad clamp) and oil tank leak (bad weld) I realized i had a marvel..

  12. #12
    Cub Builder's Avatar
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    So, what probably happened is that someone found a good buy on a MS carb and put it on there in place of the Stromberg NAS carb. It's likely that it's not the correct one for a C-85. Check the part number on the data tag, then compare it to the part number called out in the Kelly aerospace cross reference chart. The part number you are looking for is a 10-4240. If the part number doesn't match that, you've got the wrong carb. Kelly Aerospace has the engine/carb cross reference chart on line at: <http://www.kellyaerospace.com/fuel_charts/Carburetors/Facet_Marvel_Schebler_Carb.pdf>

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    [QUOTE=swoeric;515573]I have pulled my carb apart and i have found that the jet is free and clear. the mixture shaft seems to be unworn and the carb in general looks fresh and new with one exception. the inside of the carb has soot. there is soot around the jet inside and out. there is soot inside the bowl. the soot looks like black carbon from maybe a fire although no signs of heat.

    I didn't have mixture problems, but did have excessive rpm drops when checking carb heat. In my case all the soot in the carb and airbox came from a cracked and almost seperated exhaust pipe hidden by the heat muff.

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    Ok so i have tracked down some more info...the carb i have is punched 4894-a this would be an 0200 carb. so the next question..does anybody know what the jet size difference in the 4240 and the 4894 as well as the venturi size difference



    thank you

    Eric

  15. #15
    cruiser's Avatar
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    Lowes Aviation in Sacramento, KY has an STC to convert the 0200 carb to a C85 carb. They must do the work and pricey as I recall. Jim
    Last edited by cruiser; 11-02-2011 at 05:12 PM.

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    Steve Pierce's Avatar
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    Quote Originally Posted by cruiser View Post
    Lowes Aviation in Sacramento, KY has an STC to convert the 0200 carb to a C85 carb. They must do the work and pricey as I recall. Jim
    Yep I talked to them and ended up using a Stromberg. More differences than just the jet between the O-200 and the C85 Marvel.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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    tophand's Avatar
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    It's definitely pricey....Shoot it's expensive. But I sure do like it. I didn't know it was gonna cost so much, but I wouldn't trade it now.

    ......Mike

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    I've been thinking about your carb and it's issues. How in the hell does soot get into the float bowl?? The only thing that I could come up with is it must at some point been through a fire caused by the primer on the O-200, or maybe even on your C-85 before you blocked the primer at the spider. It must have smouldered for some time to cause that.
    The likely culprit causing your lean condition is the float setting must be very very low. Float setting (fuel level) is critical with these carbs and a low fuel level will need much more suction at the nozzle to get the fuel flowing, compared to a correctly set fuel level. You can check this by first shutting off the fuel supply, then remove the bowl drain plug and then install a nipple that you can slide a clear hose over. Tie the hose up so you can see where the fuel level is compared to the bowl parting line...and then turn on the fuel supply. The fuel level should fill up to about 7/16" down from the parting line for a correctly set fuel level.

    I'm not 100% certain, but the only differences between most of these carbs are nozzle sizes, idle tubes, and slight changes to the float level.
    The 10-4240 is supposed to have a 47-782 nozzle, and the 10-4894 has a 47-799 nozzle....The venturi, idle tube, float level and pretty much everything else is the same between the two carbs.
    Last edited by Pacerfgoe; 11-06-2011 at 12:16 PM. Reason: to update

  19. #19
    Steve Pierce's Avatar
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    We had a carburetor that had been in storage for some time with a black soot in the float blow. Maybe some sort of by-product of fuel over the years?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  20. #20
    Cub Builder's Avatar
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    Quote Originally Posted by swoeric View Post
    Ok so i have tracked down some more info...the carb i have is punched 4894-a this would be an 0200 carb. so the next question..does anybody know what the jet size difference in the 4240 and the 4894 as well as the venturi size difference?
    Eric, Drop me an email at <jscott.planes@gmail.com>. Sometime this weekend, I'll scan in the exploded view and parts list for these two models of the carb and email you the .pdfs.

  21. #21
    Steve Pierce's Avatar
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    So will you modify your existing carburetor to meet the C-85 specs?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  22. #22

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    Quote Originally Posted by Steve Pierce View Post
    We had a carburetor that had been in storage for some time with a black soot in the float blow. Maybe some sort of by-product of fuel over the years?
    After changing all the fuel lines from a J3 tank to the gascolator we still had soft black stuff collecting in the bowl. Turns out it was coming from a steel drain plug in the bottom of the tank. jrh
    You can't get there from here. You have to go over yonder and start from there.

  23. #23

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    the soot looks more fire related although im not seeing signs of heat..Ill take some pics before cleaning it up..Ill check the float level and report back as soon as it is in the air

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    I just took apart my friends 10-4240 and noted a few things while doing this. I also phoned a Tech at Avstar to find out a few things about the set up of these carbs.

    The thing that I noticed first about this carb is the nozzle airbleed is completely removed, and the resulting hole is .119"(other carbs are in the neighborhood of .025-.050") The technician said this is normal for this carb, and will allow lots of air to mix with the fuel thats traveling up the nozzle.
    The nozzle is a pepperbox style that goes along with the one piece venturi. Its a 47-852 nozzle with a .087" size jet. This is different than the listed nozzle on the parts break down (47-782). The end of the nozzle at the venturi end is restricted ( down to .128") compared to a regular nozzle, I figure this is so the vacuum pulse pulls air through the pepperbox end and emulsifies the fuel mixture further, rather than just pulling the fuel out of a regular nozzle end and not really mixing as well with air. The Idle tube (229-587 -.055") is the same as your carb, and everything else is pretty much the same between the carbs.
    Your original problem of no mixture control (assuming no additional vacuum leaks) must be from either a low fuel level, a loose fuel bowl, or a very lean nozzle jet.

    Whats the size of the jet in the end of your current nozzle?....Oh and whats the number on it?
    Last edited by Pacerfgoe; 11-29-2011 at 11:35 PM.

  25. #25

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    Does it have a one or two piece venturi? There is an AD to either inspect the two piece at annual, or instal a one piece replacement. Sometimes the one piece is a little troublesome so the solution is to put the two piece back in and inspect it at annual. The problems with the one piece is similar to what you described. If you want, I will swap you out for a stromberg

  26. #26

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    You ever get this sorted out????

  27. #27
    fobjob's Avatar
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    The early one-piece venturis were very rough and work fine after you polish them for an hour or so. Use the search engine. Lots of info.

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    I hate to renew an old thread but this seems like the correct spot for this. I have an O200 with the correct ma3spa carb 10-4894-1 with all the current updates that everyone hates. After fixing other engine problems and getting the float set exactly after a few trys, the carb is working fine up to almost full throttle. Past that setting, the rpm drops a few hundred and the egt's fall off. With significant leaning , the RPM's will come back up so I know it is going rich once all circuits and the main jet are pouring fuel in. I suspect this is just the typical new once piece venture richness but it is possible someone a long time ago drilled the darn mixing tube / main jet out while trying to fix a lean engine.
    I would like to decrease the nozzle size but unless I can find what the stock hole size is supposed to be, I cant even determine whether to order a new stock size or try to find a smaller tube with the updated pepper box design. So my question is , anyone know what the stock size hole should be for a 47-850 Nozzle assembly? And part two, how would I find a smaller main jet nozzle if the existing one is stock still?

  29. #29

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    Sorry I can't help with the sizes, I know how frustrating it is to find any info on this.

    If you go to the vansairforce website and search "carb nozzle sizes" there is a partial list of sizes there.
    Unfortunately your nozzle size is not on the list, but if you do find out the size could you send a note to "GrayHawk" and get him to add it to the list....

  30. #30
    skywagon8a's Avatar
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    I assume that you have this: http://wiki.ad7zj.net/wiki/images/8/...SPA_MA4SPA.pdf
    From page 16: "Assure that theaccelerator pump discharge tube is locatedinside the center ring of the venturi"
    Service bulletin # MSA-7 dated 10/11/94 covers your situation. There is a kit 666-942 to solve the issue and it appears that your carb has had this kit installed which is the installation of the 47-850 nozzle.
    I'm unable to locate the diameter of the jet openings.

    If I were you I would pick up the phone and dial:
    N1PA

  31. #31
    zenairdave's Avatar
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    Quote Originally Posted by skywagon8a View Post
    I assume that you have this: http://wiki.ad7zj.net/wiki/images/8/...SPA_MA4SPA.pdf
    From page 16: "Assure that theaccelerator pump discharge tube is locatedinside the center ring of the venturi"
    Service bulletin # MSA-7 dated 10/11/94 covers your situation. There is a kit 666-942 to solve the issue and it appears that your carb has had this kit installed which is the installation of the 47-850 nozzle.
    I'm unable to locate the diameter of the jet openings.

    If I were you I would pick up the phone and dial:
    Yes, the accelerator discharge tube is located inside the venturi but it really did not make any difference. Don't ask how I know.

    Good advice on phoning and I called them. Tech support was very helpful. It seems they start with a .0935" jet in the pepper box nozzle and when they flow test each rebuild, they drill as needed to achieve the "spec" flow. I will be a while before I can measure the existing jet but it follows that a new one will likely be the smallest they would ever expect to use. Since these tubes are about $250 in Canada, I hope to not have to try too many times. Since I also have no cut off rise, the carb guys really recommended that I get a rebuilt carb which should fix all my problems. My thinking is though that there are too many threads that say the new carb owners got was so rich that their motors did not run well. That is exactly where I am at, at full throttle position so don't see the value in doing a new/rebuilt carb.

  32. #32
    zenairdave's Avatar
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    I just grabbed a caliper to see how big .0935" is and that is a very big jet if he gave me the correct information. Certainly bigger than I was expecting.

  33. #33
    skywagon8a's Avatar
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    Am I assuming correctly that you are experimental with a name like zenairdave? If so, why don't you braze or solder the jet closed and redrill it to .0935"? Then just fine tune it until it's correct. Solder may not be correct, but you get the idea.
    N1PA

  34. #34
    zenairdave's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Am I assuming correctly that you are experimental with a name like zenairdave? If so, why don't you braze or solder the jet closed and redrill it to .0935"? Then just fine tune it until it's correct. Solder may not be correct, but you get the idea.
    I am not bound by FAA regs,
    I do not have a death wish however.
    In principle, making the hole smaller so it can be drilled out is (in principle) an alright idea but trusting that a few thousands of solder is going to stick to the old hole after I drill it out is not something I completely trust.
    I will have to decide whether to buy a new nozzle, order a new rebuilt carb or switch to an AERO Injector set up which will also work inverted.

  35. #35
    cubdriver2's Avatar
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    Quote Originally Posted by zenairdave View Post
    I am not bound by FAA regs,
    I do not have a death wish however.
    In principle, making the hole smaller so it can be drilled out is (in principle) an alright idea but trusting that a few thousands of solder is going to stick to the old hole after I drill it out is not something I completely trust.
    I will have to decide whether to buy a new nozzle, order a new rebuilt carb or switch to an AERO Injector set up which will also work inverted.
    Egg the hole out before soldering. I'm guessing you never hot rodded any cars, bikes, sleds or...........................when you were younger. This is the same carb that came on your grandfathers Farmall when he got back from the war. Simple fix if you can't find new. If nothing else it will tell you what size jet to buy

    Glenn
    Last edited by cubdriver2; 12-02-2016 at 11:28 AM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  36. #36

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    Not to get too technical on jets but the entry and exit angles of the hole also affect flow.That said I would solder it and drill it to what I thought was close then buy the correct jet if it worked out.Another way to plug it is to press a piece of rod into it then drill your hole.Both methods would require drilling oversize first.

    Bill

  37. #37

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    If you want adjust carb jet, I would say the first thing you would need is a 4 cylinder egt/cht. Fuel flow and map would be nice also. Go fly the plane and figure out what you have. Now pull the carb and jet. Get a fine drill bit index and figure out what bit fits the nozzle. Take the next bigger bit. Put drill bit in vice and by hand turn nozzle onto bit, once drilled rotate nozzle in reverse to smooth out jet. Put on plane and test. I have a friend that had a buddy that i don't remember the name that did it 18 times!! He would do it again!! What do you have more of time or money!!

    Sometimes it is as simple as going to the old guys that have hangers full of stuff including small stock of nozzles that you can trade out!!
    DENNY

  38. #38

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    I was thinking about your carb troubles today at work, and I wondered if that carb has the "economiser" feature. It's a air channel that applies a vacuum signal to the float chamber area. In full throttle conditions the float chamber is exposed to ambient atmospheric pressure, and anything other than full throttle, the butterfly valve creates a vacuum signal that reduces atmospheric pressure and therefore flow out the main nozzle.
    So in your case, if the hole in the nozzle is to big it would have restricted flow at anything less than full throttle, and at full throttle it would flow like gangbusters.....

    Something to think about...

  39. #39
    skywagon8a's Avatar
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    Pacerfgoe,
    I think that you are thinking about the small Stromberg carburetors. They use back suction for mixture control.
    N1PA

  40. #40

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    Quote Originally Posted by skywagon8a View Post
    Pacerfgoe,
    I think that you are thinking about the small Stromberg carburetors. They use back suction for mixture control.
    No, I'm talking of the Marvel Scheblers. The carb I have on my Pacer has this feature.

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