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How to measure float height in carburetor bowl - Honda BF20D 2005 - Electric Start

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  • How to measure float height in carburetor bowl - Honda BF20D 2005 - Electric Start

    I am experiencing low speed and idling problems, so I have dismantled and checked and cleaned out the idle air screw and passages, along with main jets, nozzles and accelerator pump, according to the workshop manual. Also checked the resistance of the SE Thermal Valve and that comes in right on 20ohms (spec 15.8 to 22.4Ohms is permitted). I also found a leak in the fuel chamber vessel (a hairline crack) which I have repaired.

    However the float height is puzzling me because the manual diagram shows the measurement (13mm / 1/2 inch) being taken beside the arm on which the float floats pivots, which really doesn't move all the much, whereas the part of the float furthest away from the arm (pin) is liable to move over a much wider range, and that measurement is much less than the 13mm stated. If I work off this measurement, I would suspect there is too much fuel in the bowl. I am using the plunger on a vernier caliper measure the height (as I always do) rather than the specific Honda measuring tool. Can anyone shed any light on this?

    1) Is the split in the fuel chamber vessel likely to cause low speed running problems?
    2) Where should I take the float height measurement?
    3) Is it worth checking valve clearances to solve erratic idling?

    Many thanks!!

  • #2
    Re: How to measure float height in carburetor bowl - Honda BF20D 2005 - Electric Star

    Bump.. Still Experiencing Slow speed problems. Erratic idling and adjusting fuel screw doesn't seem to make any difference. Motor seems to be running way too rich. Does the position of the SE valve make any difference? What else do I need to check..suspected leaky inlet manifold..?? Would incorrect float height cause poor and erratic idling?

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    • #3
      Re: How to measure float height in carburetor bowl - Honda BF20D 2005 - Electric Star

      Hi Steelstrings,

      Did you sort out how to measure the float height? I have the same question - measuring near the pivot, as indicated by the manual, seems odd as there is very little movement there.

      I have 2 BF10s (for a sailing catamaran). I can't get any response from one carburetor. I know the problem is neither electrical nor fuel pump, lines nor fuel itself as with one carb the engine starts and runs fine whereas with the other I can't get anything. The bowl has fuel in it so I doubt it is a float problem - but I'd like that measurement to be correct. The only problem I can find with any of the internal workings of the carbie is an accelerator piston that is stuck. That this would prevent an engine from even kicking over seems improbable.

      Rovert

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      • #4
        Re: How to measure float height in carburetor bowl - Honda BF20D 2005 - Electric Star

        Originally posted by Rovert View Post
        Hi Steelstrings,

        Did you sort out how to measure the float height? I have the same question - measuring near the pivot, as indicated by the manual, seems odd as there is very little movement there.

        I have 2 BF10s (for a sailing catamaran). I can't get any response from one carburetor. I know the problem is neither electrical nor fuel pump, lines nor fuel itself as with one carb the engine starts and runs fine whereas with the other I can't get anything. The bowl has fuel in it so I doubt it is a float problem - but I'd like that measurement to be correct. The only problem I can find with any of the internal workings of the carbie is an accelerator piston that is stuck. That this would prevent an engine from even kicking over seems improbable.

        Rovert


        Hi Robert...
        Didnt get a response.
        Since you have 2 motors, could you drain and measure contents of both carbs? This should tell you if the floats are set the same.

        Steelstrings.

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        • #5
          Re: How to measure float height in carburetor bowl - Honda BF20D 2005 - Electric Star

          Good suggestion re measuring fuel volume in both carbs - thanks.

          Having freed the accelerator piston I was able to get it running reasonably well yesterday. Idle was OK, though it can vary quite a lot while with no input.

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          • #6
            Re: How to measure float height in carburetor bowl - Honda BF20D 2005 - Electric Star

            That's the same problem as I have - irregular erratic idle without touching the throttle. I suspect there must be some worn parts in the carb..but be nice to hear from the experts on the forum??

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            • #7
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              Re: How to measure float height in carburetor bowl - Honda BF20D 2005 - Electric Star

              Don't know about Honda carbs; you must turn carb upside down and have float parallel to carb's edge, are needle and base in opt state ? probably are worn out and float is not resting where it should ? Asume a 4 strokes, check valve clearance, just in case.

              Happy Boating


              Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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