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  1. #1

    Can't beat lean condition - video included

    I couldn't get my 1200 SUV out of a lean condition with the low screws all the way out. It would idle fine but giving it 1/2 to full throttle would either kill it or hold it around 3k rpms and then drop down and die unless I released the throttle.

    When I could get consistent rpms around 3k-4K, it was missing/backfiring little pops. Then, when it "caught" around 4K it shot off like a rocket but never got rpms over 5,800 and top speed of 40.

    I couldn't seem to get a difference out of adjusting the low speed screws. Same behavior 1 turn out to 3 (full out). I have fuel in the return line. All hoses are connected well and secured. I'm at close to 12,000 ft and I do not know how the oxygen would affect the carbs.

    So to recap, here are the changes from start to finish... Rebuilt carbs, performed pressure balance mod, replaced 1.2 main jet with 1.5, pop off pressure of 62 psi, replaced carb fuel link hoses and pulse hoses.

    Here are links to video of this on the water today...





  2. #2
    jeffg426690's Avatar
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    Stock air intake?

  3. #3
    Quote Originally Posted by jeffg426690 View Post
    Stock air intake?
    Yep, stock. I was running during this particular time with the F/A's off because I was constantly in adjustment mode and had the carb cover off multiple times.

  4. #4
    With the pop off pressure at 62 psi in high elevation and lower air pressure, is it logical the pop-off should go down? With this thin air, it naturally lends itself to a rich mix so it makes more sense that pop-off is the problem.

  5. #5
    Also, I performed the pressure balancing mod. Would elevation have any impact on the choice of the 105 jet as instructed by Bill? Could it need a bigger jet?

  6. #6
    jeffg426690's Avatar
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    Quote Originally Posted by jhawker23 View Post
    Quote Originally Posted by jeffg426690 View Post
    Stock air intake?
    Yep, stock. I was running during this particular time with the F/A's off because I was constantly in adjustment mode and had the carb cover off multiple times.
    Running w the stock FA & intake off = LEAN - esp w stock pilot jet
    On the top side, if your still running stock air intake why did you change the main jet to 1.5?
    Return mod, I believe Bill started a w a 95 pilot. Going to a 105 will lower your pressure.

  7. #7
    butterbean_29512's Avatar
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    Always reinstall the flame arrestors, whether they are stock or aftermarket, before you test after carb adjustments.

  8. #8
    Quote Originally Posted by jeffg426690 View Post
    Quote Originally Posted by jhawker23 View Post
    Quote Originally Posted by jeffg426690 View Post
    Stock air intake?
    Yep, stock. I was running during this particular time with the F/A's off because I was constantly in adjustment mode and had the carb cover off multiple times.
    Running w the stock FA & intake off = LEAN - esp w stock pilot jet
    On the top side, if your still running stock air intake why did you change the main jet to 1.5?
    Return mod, I believe Bill started a w a 95 pilot. Going to a 105 will lower your pressure.
    Thanks Jeff, the change to 1.5 was at the recommendation of many and they needed to be replaced due to age and wear. Nearly everything started at 1.5. I went back and checked Bill's post and it instructed a 105 jet. With less air pressure, a 95 jet could be more appropriate? I have so many changes going on at once I need to step back to one at a time. So I'm going to start with pop off pressure and reduce down from 62 psi. I'm also at a stock 135 main. According to a Mikuni slide tool, the combination of elevation and temperature nets a reduction to a 127 main. So I have that on the way. I also ordered some 95s. So I'm able to change the return jet if necessary. I also wanted them in case I needed to step down from 100 slow jet. I don't see as much info on the slow jet vs. main.

  9. #9
    jeffg426690's Avatar
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    Oside recipe calls for aftermarket FA's, not stock intake. Reading through that post you'll see that no one ever came up w a good combo to rejet w stock air. Stock air vs aftermarket FA's vs nothing at all : substantial difference between all three.
    I'd think about sticking to the recipe to the T, complete w FA's and 105 or 110 low depending on choke and 1.5 N&S.
    Then tweak from there if necessary for altitude

  10. #10
    I'll add aftermarket FAs. Any recommendations?

    This has been the most expensive, longest, most frustrating "easy improvement" I've ever had. This started with a simple carb rebuild and has completely gone down the rabbit hole.

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