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  1. #1

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    O.S. LA 15 carb problems

    Members of my club and I fly SSC using OS LA .15 engines. With the "occasional" mid-air collision and the yard darts that result, we have seen a problem with the small black plastic "spray bar and pressure fitting" that fits into the side of the carb on the LA 15 engine. In some of those mid air paint transfers, the fuel inlet nipple breaks off or the black plastic spray bar snaps off at the carb, or they just fall out. In order to make the engine usable again, you have to replace the entire carb ($22.99) or the carb housing ($11.99) which comes with the spray bar and pressure fitting (probably about $.10 of plastic), and then take everything off the old carb and switch them out and hope you can get it back running after changing all the idle settings. Has anyone else encountered this problem, and does anyone know if there is a better solution to replacing the failed piece with the same piece that's just waiting to fail???

    Thanks
    "Grinder"
    DO WHAT YOU DO BEST & HIRE OUT THE REST

  2. #2
    Blue Note's Avatar
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    RE: O.S. LA 15 carb problems

    Interesting. I too have run some of the O.S. .15 's but have not encountered that exact problem ( yet ). Some will say to switch to the Magnum .15, but it has its' own set of issues and you already own the O.S. Unfortunately, I have no proposed solution, but you may want to also look through the RCCA website, if you haven't already, here http://www.rccombat.com/forum/default.asp. There is not a ton of daily activity there, but it is very specific and checked by the members often. A new posting there may reach the right peoplethere pretty quickly. Keep us posted here if you find the solution. Good luck.
    BNC

  3. #3

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    RE: O.S. LA 15 carb problems

    Grinder,
    The repair is pretty easy. The plastic nipple assembly is a press fit into the carburetor body. You can usually grab it with a set of slip joint pliers and work it out. Next take a 2” length of copper tubing like is used in the fuel tank and carefully bend to a 90 deg. angle insuring that you do not generate any crimps. I usually bend it around a screwdriver handle or something similar. With a Dremel tool cut off about ¼” of the end that will fit onto the carburetor and bevel the end at about 45 deg. so that it fits the hole nicely. This will keep it from sticking out too far and provide a tight fit for the next step. Next JB Weld the new copper nipple to the opening in the carburetor being careful to keep the needle end pointing toward the needle valve. Be generous with the JB Weld. You may have to sit and hold it for a few minutes while the JB Weld sets up. I have never had one to fail after this repair.

  4. #4

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    RE: O.S. LA 15 carb problems

    Regent,

    Thanks for the reply. It's early and I'm still waking up so you'll have to forgive my for my confusion. So you discard the black plastic "original equipment spray bar & pressure fitting" all together and create your own spray bar from the copper tubing and JB weld it in place of the black plastic OE spray bar??? To clarify, you take a 2" piece, bend it 90 degrees, estimate the depth into the carb body and then cut it off and create a 45 degree angle on the end going into the carb body at the approximate length, hold it in place and JB weld the copper tube into the original spray bar opening, holding it in place until it's firmed up??? If I'm following you correctly, it would seem like it would work. Taking that idea further, have you ever attempted to drill out the original spray bar housing to the diameter of the copper tubing and used the original body as a guide / shim to hold the tubing in place? Do you have any pictures of one you have done?

    Thanks for the idea. I sent out a couple of e-mails to O.S. to see if I can order just the spray bar portion, but haven't heard anything yet. Thanks again.

    Grinder
    DO WHAT YOU DO BEST & HIRE OUT THE REST

  5. #5

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    RE: O.S. LA 15 carb problems

    Grinder,
    No, I don’t replace the spray bar, just the plastic nipple housing. I JB Weld the copper tubing to the end of the spray bar.

    After you remove the plastic nipple housing from the carb you will see the end of the spray bar. Once you take it apart you will see what I am talking about.

    Unfortunately I recently sold all my SSC combat engines to a club member so I can’t post any pictures. I have done this repair to 3 engines total, 2 of mine and 1 for a friend.

  6. #6

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    RE: O.S. LA 15 carb problems

    I've had problems with the plastic part that feeds into the carb you're talking about falling out of the carb too. What I do to avoid the situation altogether is before I even run an OS 15 LA for the first time I really go through it to avoid some of the weaknesses in the engine. One thing I do which has solved your problem is I put JB weld over the joint where the black plastic part joins with the carb. This will prevent it from slipping out, which it will invariably do with time. I also replace the plastic backplate with a metal one, sealing it with hi-temp gasket goo (I forget the name at the moment). I also replace all the screws in the head, backplate, muffler, and carb with socket head bolts so I can remove the screws easier with an allen wrench if necessary. Drill out the baffle to increase RPM's. A lot of great tips on break-in procedure, etc can be found at this website: http://www.georgiacombat.com/OS15EngineSetUp.htm That website has been REALLY helpful to me.
    Hope that helps,
    Dr. Andy Runte aka "Dr. Kamakaze"
    of -TEAM KAMAKAZE-
    RCCA #876
    AMA #273119

  7. #7

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    RE: O.S. LA 15 carb problems

    Dr. Kamakaze,

    Thanks for the reply. Those are all good suggestions. I know a few guys have gone to the JB Weld on the spray bar before they ever instal them on the airframe. We just see alot of the inlet nipples getting snapped off (50%) and completely sheering the spray bar / pressure fitting off at the carb the other 50% of the time. I can live with it backing out, at least the part is still intact and with a small zip tie, I can make a quick field fix and get back in the furball. With an amputation, I'm sitting on the sidelines or playing event timer. Never fun to watch combat once you've flown combat. We have also gone to removing the OE back plate, but rather than switching it out, we cut off the needle valve portion on a band saw, RTV gasket the OE backplate in place and use a washer under each screw head to re-install it to prevent leaks. As for the needle valve, we re-locate that by either zip tying it to the motor mount or a bracket on the fuse, or by going to a different remote needle valve all together (FP 60). Haven't heard of replacing the head screws by anyone in our club, but I could see the benfits if you have one that likes to loosen up on you. As for boring out the muffler, many have done mods to that, but we are all limited to 17,500 RPM, so once I'm getting that out of it, I'm happy and just look for ways to get down to weight minimums.

    Another guy and I may try Regent's suggestion or a variation of it and see how it turns out. We'll probably have to wait until next season to see how it works because this weekend looks like it might just be our last combat weekend until next spring, but who knows... there is always Indian summer (maybe???) As for tomorrow, I'm venturing to the LHS later to pick up a pair of OS carb housings with the OE spray bar pre-installed. That will at least get me off the bench tomorrow.

    Thanks again & Take care!
    Grinder
    DO WHAT YOU DO BEST & HIRE OUT THE REST

  8. #8

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    RE: O.S. LA 15 carb problems

    Socket head screws are nice, but you can use the stockers if you get the correct screwdriver. The head bolts, backplate bolts, and carb rotor retaining screw (the little teeny one) are JIS, NOT Phillips! A phillips driver will not work well in them, but JIS will grip them very well. On the other hand, for some reason a #2 phillips works best on the carb mounting screws, the muffler bolts, and the muffler thru-bolt.

  9. #9

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    RE: O.S. LA 15 carb problems

    If the little spray bar extention is damaged, no problem. I've put a short piece of metal tubing into the throttle housing "as is" and it works fine. I use regular brass fuel line from the scrap after fitting tanks. I bring the tube just to the edge of the venturi and fix it in place with JB Weld.

  10. #10

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    RE: O.S. LA 15 carb problems

    lol I think after almost a year, he probably figured it out or got another engine


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