Carburetor Troubles? 2F is sputtering

Discussion in '40- & 55-Series Tech' started by cruiserhead75, Feb 21, 2009.

  1. cruiserhead75

    cruiserhead75

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    I recently rebuilt the carb on my 1976 40. After fixing the float level and getting it within the little dot on the glass, the cruiser rev's very nicely and idles fine. But when I go to drive it, it sputters and almost dies. The only way to get it up to speed is to pump the throttle. I suspect that the secondary is not opening. Could this be my provblem? I have also tried leaning it out and richening the mixture screw, it seems to run better when leaned out, but still sputters and has not power or smooth acceleration.
     
  2. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    The mixture screw only trims the idle fuel. Should not have a significant effect on main circuit driveability.

    If pumping the throttle "tricks" it into running good, then the accelerator pump shot is adding the extra fuel to make it run right for a second. Therefore the carb is too lean for some reason. Look for junk stuck in the main jet or emulsion tube.

    The secondary is not opening because the engine is not running right. The primary barrel needs to run strong enough to wind up the engine and require the vacuum actuated secondary barrel to open.
    In this case a lack of secondary operation is a symptom, not a problem.
     
  3. cruiserhead75

    cruiserhead75

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    where is the emulsion tube located in relation to the main jet? also, is the scondary jet bigger than the primary?
     
  4. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    emulsion tube is pressed into the bottom of the booster, dips into the main well.

    Sec jet is prolly 230, pri is prolly 144.
     
  5. Pin_Head

    Pin_Head

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    When it sputters, put it in neutral, let it die or turn off the key, and pull over and check the fuel level in the bowl. Did it run out? If so, there may be a fuel delivery problem.

    Did it do this before you rebuilt the carb?
     
  6. cruiserhead75

    cruiserhead75

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    i pulled the top off the carb, pulled the drain nuts off the bowl, and blew out both of my jets, and all galleries that can be purged from that position. I still have major sputtering when i drive the cruiser. What am i doing wrong?
     
  7. cruiserhead75

    cruiserhead75

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    The level in the bowl is fine. I have also checked my fuel pressure, it is ok. The sputtering was not an issue before i rebuilt the carb. When I start the Cruiser, it idles excellent, and revs good. It only has a problem when i try to drive it.
     
    Last edited: Feb 21, 2009
  8. Pin_Head

    Pin_Head

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    If you are sure that the fuel pressure and volume are fine and it isn't running out of gas under load and it didn't do it before you rebuilt it, then chances are you screwed up the rebuild. It isn't getting enough fuel out of the primary main nozzle.

    Try rebuilding it again. Clean it in carb dip, rinse well, blow out all the tiny holes with compressed air or carb cleaner spray. Verify that all the passages are clean and open and that there is not dirt or grit floating around in there. Reassemble properly and adjust to specs in the FSM. It should run fine on only the primary. The secondary only opens when you put the pedal to the metal.
     
  9. cruiserhead75

    cruiserhead75

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    I am certain that it IS running out of fuel under load. When take-off is attempted, the car sputters and almost dies. The tailpipe does not smell rich at all. I may need to rebuild the carb again, although i am almost certain that i did a quality rebuild. I soaked all parts in chem dip, and blew out all passages. Every part was replaced, every passage cleared. The only thing that could cause this must be debris. I am going to pull the carb off one more time and try to clear everything out once more.
     
  10. bsmith123

    bsmith123

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    advance

    did you remember to hook up the vacuum advance?
     
  11. Pin_Head

    Pin_Head

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    That is why I asked you if the bowl is empty when it "sputters and dies". You seemed to be sure that it is full. If the inlet is clogged or the pump is weak or fuel supply is clogged, then the fuel delivery can't keep up with demand. If your bowl is full when it dies, then the problem is delivery from the bowl to the nozzle. Fuel starvation is usually accompanied with bucking and spitting back through the carb, which is what I hear when you say sputtering.

    If it was a mechanical advance issue, it wouldn't rev well load or no load.
     
  12. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    Make sure the slow jets, main jets and boosters are in their correct primary/secondary locations.
     
  13. igotta40

    igotta40

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    I'm in the same situation. Mine feels like it's not getting gas, but only when accelerating on the primary circuit. Sight glass level is actually a little high. Running with choke pulled or with secondary open, it runs fine, no bucking and backfiring into the carb, with the accompanying smell of unburnt gas. After reading the threads and thinking real hard, I thought maybe the carb came with a high altitude primary jet, but the odds of that seem slim.

    So I thought the problem (mine and the OP) might be an air leak small enough to only affect the primary circuit.

    Rather than running out of gas, it may be too much air, right?
    Sound realistic?

    I'm going to pull my newly rebuilt carb and chaeck it over then post back up here.

    The motor is a newly rebuilt 2F Oct 1975, carb is April 1972.
     
  14. fireflyr

    fireflyr

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    I rebuilt my Weber 32/36 and faced the same issues. I finally came to the conclusion that I had incorrectly re-installed my main jets and also the air corrector jets. I'm not sure if that is an option on the stock carb.
    Thru this process I ended up rejetting the carb and it runs better than ever. The problem you're describing sounds like the rich/lean issues I was dealing with.
     
  15. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    Could be air leakage, through the leaks at the warped flanges on top & bottom of main casting.

    Next time it is apart, press the flanges straight on the main body and air horn.

    It is also very possible the F carb is too skinny for a fresh 2F.
     
  16. igotta40

    igotta40

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    Thanks Jim, good insight. I thought about the fact that a carb for an F may be inadequate for the larger displacement 2F, if that's what you mean by 'skinny'. I had the same problem before I got the motor rebuilt, but the case could still be made. Though I don't see posts from guys who replace an F with a 2F having fuel starvation problems.

    If I don't find any air leaks I'm going to start changing primary jets, if I can locate any.

    Thanks
     
  17. cruiserhead75

    cruiserhead75

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    Jim, i have taken my carb down again and soaked everything in chem dip and blown everthing out with compressed air. after realizing that my power valve piston was being restricted, i turned the retaining clip the other direction. I also replaced my fuel filter before putting the back on. Now my cruiser drives OK when you baby it, but when i give it a good amount of throttle, it sputters and has a lack of power. i also noticed that in the breif jont around the block, it has been running warmer than usual. Could i still be running lean? Also, i do not know the technical name for the part, but the piece(s) that go in the middle section of the carb that direct gas down the barrels, one has a ring around it, the other doesn't. I think they are the venturi's? one has a 4, the other has a 6 on it. which is primary, which is secondary. BTW You were dead on when you suggested what my jet size might be.
     
  18. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    The boosters are mounted inside the venturi. They boost the vacuum signal at the nozzle.

    The single ring booster goes in the secondary.
    Double ring booster is the primary.

    The numbers on the boosters are meaningless. Just a mold number.
     
  19. cruiserhead75

    cruiserhead75

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    Sure enough, i had my boosters switched from the begining, along with a restricted power valve. From here on out, it's fine tuning. Thanks Jim!
     
  20. igotta40

    igotta40

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    Guys, hope ya'll don't mind me piggybacking in this thread but it's helping me a lot. Reading that part about the venturis got me looking back at my rebuild. My carb came with two double ring venturis. So the secondary venturi is the wrong one, but I'm not having a problem with the secondary. Just interesting, that's all. Rebuild factory worker must have grabbed the wrong one out of a parts basket. Makes me wonder what else could be mixed up. It's a TOMCO carb. I got my hands on some jets from a fellow cruiser guy so I'll try some experimenting. I still have low power and hiccuping and I'm tired of it.
     
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