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  1. #1
    j301's Avatar
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    Walbro WT 610 help

    I'll try to make a long story as short as possible: Came across an older engine (webra bully 35) and while getting it back into shape I replaced the old HDA 48 with a WT 610. Didn't run, rebuilt the carb, then it would only run on prime then die. Dinked around with that for a while, finally replaced the 610 with a WT 540 and all was good, figured the 610 was bad. Came across another oldie, a Quadra 50, and decided to see if I could get it going. Stock carb, not running, stock rebuild, not running, just for fun I put the old bully HDA 48, it ran but not good. Thought I'd try the WT610 just to see what would happen and it was an exact repeat of the bully-run on prime then die. At that point it told me the ignition was good, and I could feel it had good compression so I thought I would try another new WT 610 as you cant really get the 540's any more. The carb was new and had not seen fuel, plug it in, and guess what,,,,run on prime,,,die. Took the new diaphragm kit from the recently rebuild original 610 and put it in new 610, prime-run-die-lather-rinse-repeat. And this is after playing pin-the-tail-on-the-high/low needle-settings for an hour. So for fun I threw on the WT 540 from the bully on it, and VVVRRRRROOOOOOOOOOOOOOMMMMM, ran like a top, telling me its the carb...

    So my question is this; is there some Walbro ritual I am not aware of when it comes to the WT 610? Perhaps something involving an old hubcap, some chicken bones, and an open flame that must be performed on the last Wednesday of the full moon cycle? Is the 610 a POS, or was I lucky enough to get the 2 that comprised the .02% of the acceptable factory failure rate? (meaning I should have bought some lotto tickets instead...)
    Any help would be appreciated,
    Thanks!
    ARF\'\'s; because it\'\'s less depressing to take out a box of plane and bring back a box of sticks.

  2. #2
    Moderator w8ye's Avatar
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    RE: Walbro WT 610 help

    Sonds like impulse signal to the carb problems
    Attended the CutFinger Institute of DirtNap University for years but never did graduate....
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  3. #3
    earlwb's Avatar
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    RE: Walbro WT 610 help

    Sounds like you aren't getting the crankcase pressure pulese to the pump diaphragm in the carb. You accidentally blocked it off somehow.
    How do the crankcase pulses get to the carb's pump diaphragm in your setup?
    Some engines use a crankcase fitting and tubing to route the pulses to a fitting on the pump cover. Other engines route the pulses up through a carefully drilled hole through the carb base gasket into the carb where it is routed over to the pump diaphragm.
    Some engines used the crankcase pressure fitting to route the pulses to the carb adapter plate where it was routed up through the hole in the carb base gasket.
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  4. #4

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    RE: Walbro WT 610 help


    ORIGINAL: w8ye

    Sonds like impulse signal to the carb problems
    Or perhaps a wrong or improperly installed pump diaphram.

  5. #5
    av8tor1977's Avatar
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    RE: Walbro WT 610 help

    Might not be an impulse problem if it runs on another carb.

    Look at the mounting face of the problematic 610 and see if it has a pulse hole in it next to the carb throat. If so, see if it is open from there into the fuel pump chamber.

    Then remove the high speed needle and blow some WD-40 in the hole while looking into the throat of the carb. You should see the WD-40 squirt into the venturi of the carb. If that works, then squirt WD-40 in the various holes in the regulator chamber of the carb. One of them should feed the high speed needle, and you should see the WD-40 squirt out of the high speed needle valve hole. If all goes well, screw the high speed needle valve back in, and do the same process for the idle needle.

    I used to use carb cleaner spray to rebuild carbs and to do the above exercises, but then it started ruining the various check valves in Zama carbs. Carb cleaner spray works ok in Walbro carbs, but just in case they change the material in their check valves, I decided to use only WD-40 for all the carbs I service.

    AV8TOR
    If it is not SCARY, it is NO WHERE NEAR powerful enough!!
    All R/C planes have expiration dates---> It's just not printed on them anywhere!

  6. #6
    j301's Avatar
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    RE: Walbro WT 610 help

    Thanks everyone for you help so far. I checked the pulse port and its not being blocked by anything. I also blew wd40 thru the ports and everything on the high side worked. On the low side it did not blast thru the same holes though. When squirting the through the low speed needle hole (yup, breaking out the tech terms now!) it would come out the inlet needle valve and not through the venturi that I could see. I also double checked the walbro web sight to make sure I put it back together right. I noticed that the IPB

    http://wem.walbro.com/walbro/product...rtnum=WT-610-1

    shows a part # 33, surge diaphragm, that neither carb had, nor did one come in the kit (k20 wat). I kept all the extra parts from that kit and am looking at them now, and I dont see it. Sounds like a part one would need doesnt it? Or is this something to do with primer pump section that this carb doesnt have? Neither 610 came with the fuel pump spring either. I know walbro makes a hundred variations for a thousand motors, so its king of hard to tell what a generic version is supposed to have when researching a specific parts list.
    ARF\'\'s; because it\'\'s less depressing to take out a box of plane and bring back a box of sticks.

  7. #7

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    RE: Walbro WT 610 help

    I doubt your carb needs that surge diaphram. You certainly need the pump diaphram and the thick gasket that goes between the diaphram and the cover plate though.

  8. #8
    j301's Avatar
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    RE: Walbro WT 610 help

    ORIGINAL: Truckracer

    I doubt your carb needs that surge diaphram. You certainly need the pump diaphram and the thick gasket that goes between the diaphram and the cover plate though.
    Ya I have that, and just looked for some kits on line and none come with the surge diaphragm. Its odd, two 610's, both not working the exact same way, both pre and post rebuild, both on multiple motors that run on other carbs. Maybe the are somehow just not the right size or design for this kind of motor? Anyone know what the next in line to replace a 540?

    Or even just a good carb for a Quadra 50?
    ARF\'\'s; because it\'\'s less depressing to take out a box of plane and bring back a box of sticks.


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