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Thread: Carb adjustment question

  1. #11
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    Quote Originally Posted by pisten-bully View Post
    Whoa... 303 Autolite plugs work well in my Chief...don’t go bad mouthin’ my plug choice!
    Good for you, Harry!

    What kind of coil/ignition are you running?

    ...Cotten

    Quote Originally Posted by Lipdog View Post
    Yeah, I get your point about chasing problems. But I don't think this carb is right. I swapped in the J6's, drained the excess oil from the sump, and got it started (for the first time, hot as well as cold). When I turned the LS needle in all the way, the bike still ran ok. Revving it a bit and checking the HS needle, it didn't seem to have much of an effect. And it fouled the plugs after a few minutes (see photo). I pulled the carb and will check the manifold for leaks this weekend, just to be sure.
    Measure the LS needle length out of the knob, Jeff,..

    The 1/4"-40 threads means a lot of turns to make up any shortening at all. And they do get dressed, of course.
    (Here's one from the ebay hero sold as new. I've got a pic of one of his new HS that's knicked, too.)

    ....Cotten
    PS: Can't tell much from your assembled pics, but face it, an M344 ain't finished if it ain't black..
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    Last edited by T. Cotten; 09-20-2019 at 09:22 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  2. #12

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    The LS is 3-3/8" long, and the HS is 2-2/4" long, measured from the bottom of the thread, as shown in the pix.

    If I were to start by replacing some parts on the carb to get it in range, where would you start? I was thinking at a minimum I'd replace both needles with new ones, and gaskets.
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  3. #13
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    Quote Originally Posted by Lipdog View Post
    The LS is 3-3/8" long, and the HS is 2-2/4" long, measured from the bottom of the thread, as shown in the pix.

    If I were to start by replacing some parts on the carb to get it in range, where would you start? I was thinking at a minimum I'd replace both needles with new ones, and gaskets.
    Since the LS is our immediate concern, Jeff,..

    Please remove the screw, lock, and spring, to measure the needle's length from the bottom of its spring "head".
    I have found great variance in the 'fossil record'. Graciously they are adjustable.

    Rarely did I ever retail a new needle (Got plenty!)
    Throwing parts at it doesn't help if the new stuff needs re-worked anyway.

    First patient observation and inspection: Take it all the way apart and let the gremlins out.
    Any stone unturned gives you another tail chase.

    Looking forward to the bubble-test..

    ....Cotten
    PS: Every turn on the knob is .025".
    So the difference between three and a half turns and seven-eighths is just over a sixteenth of an inch.
    Look for grinder marks.

    Or hope like Hell nobody took a drill bit to your LS seat. I can't help much then... sorry...

    PPS: "Within range?"...
    Are you just getting it ready to sell?
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    Last edited by T. Cotten; 09-20-2019 at 01:49 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  4. #14

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    I rigged up a pretty basic rubber stopper with am air fitting threaded in, greased it with Super Lube, and held it firmly in place while I pressurized the intake manifold to about 12 PSI with the bike on the compression stroke. I then sprayed soapy water on the manifold nuts. I couldn't see any bubbling at all, and the pressure bled down *very* slowly, maybe a few PSI per minute. This could have been through the cylinders or through my rig, but everything seemed very tight. Does this seem ok?

    Next I measured the LS and HS needles. The LS needle is 3.43" from the seating surface at the top to the tip. The HS needle is 2.75" from the bottom of the screw threads to the tip. I also photographed what the HS seat looks like with the needle 3.5 turns out, and what the nozzle looks like.

    The low speed lifter washer/spacer is brass and seemed to be in the correct way.

    Does anything stand out here? What would you check next?

    IMG_0376.jpg

    IMG_0378.jpg

    IMG_0384.jpg

    IMG_0381.jpg

  5. #15
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    Its not about "bleed down", Jeff!

    Its about pressure differential, and that's why a constant, regulated supply is essential to make bubbles.
    The gap between the valve stem and guide alone is an order of magnitude larger than the holes we are looking for, and frankly, it isn't that easy to get both intakes shut on some Chiefs.

    So we know your LS needle is 2.8 turns of the knob shorter than it should be.
    (Nice Schebler/early HD Linkert screw on top! Worth a dozen 'correct' ones. Both knobs are pre-'48... and that looks like a shorter detente spring.)
    If it was adjustable at all, its probably not the cause of fouling.

    Unless completely shut, the HS needle does not affect idle mixture at all.

    It might be just the pic, but the nozzle spigot looks short.
    It should reach just shy of the middle of the bore.
    Even that shouldn't cause fouling, by itself.

    I see you have a correct gallery plug, but the bowlstem looks crusty to me. Please completely disassemble, and inspect the idle bleeds for obstruction, and clean with a .008" feeler gauge narrowed to a sixteenth of an inch or so.

    And please don't forget the bowl assembly is a "circuit" of its own.

    ...Cotten
    PS: If its got throttledisc wear anything like my second pic bottom right, its always going to be difficult.
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    Last edited by T. Cotten; 09-21-2019 at 12:15 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  6. #16

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    I took it all apart and cleaned it with carb cleaner and compressed air. The only issue I could find was that the float was set about 1/8' too high, so I corrected that and put it back together. I can't think of anything else, so I'll start it up and see what I get.

  7. #17
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    What kind of float was it, Jeff?

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  8. #18

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    I don’t know exactly what it’s made of, but it’s black hard, hollow plastic, if that helps. Thanks,
    Jeff

  9. #19
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    Quote Originally Posted by Lipdog View Post
    I donít know exactly what itís made of, but itís black hard, hollow plastic, if that helps. Thanks,
    Jeff
    Well, Jeff,..

    The carb was designed to use a three gram float.

    What's it weigh?

    (If the pivotnut is molded-in, its not only a boatanchor to begin with, but prone to swelling.)

    ....Cotten
    PS: An example is shown on the left in the attachment; On the right is a float of proper buoyancy, but still swollen by fuels unknown.
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    Last edited by T. Cotten; 09-22-2019 at 11:39 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  10. #20

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    It weighs about 8g (see photo). I'm ordering some parts, which one should I specify to replace it with? I'm going to get the LS needle that's the proper length too. Thanks!

    IMG_0388.jpg

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