Whistling BG Carb
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Whistling BG Carb

  1. #1
    Senior Member Rivernut's Avatar
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    Default Whistling BG Carb

    Got my BG set-up running well, but it has whistled since putting it on. I tried lithium grease on the base gasket, then two base gaskets, still whistles. It does it at part throttle. It is loudest when backing off from full throttle. I sprayed starting fluid around the carb and intake at idle, no change in idle. I put a restrictor in the PCV line, no change. The two vacuum other ports are capped. It sounds sort of like blower or turbine whine, like a loud hiss. The carb is a 650 Marine Demon vac sec. I noticed the accelerator pump discharge hole with no screw in it, so I assume it's not coming from there? Do these carbs with down-leg boosters hiss? I tightened the baseplate screws before installing it. Do these leak around the throttle shafts at high rpm's? What gives?
    Last edited by Rivernut; 09-02-2010 at 03:14 PM.

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  3. #2
    cfm
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    Very normal with these carbs as the secondaries are opening or just closing. I refer to the noise as a 'momentary belt slipping noise.' But yes, it's a whistle.

    As mentioned in your other thread, I've used/installed a few of these.

    If you change the spring in the secondaries you'll hear it at a different rpm, thus knowing it's the secondaries.

    Again, it happens when the secondaries are opened just past the 'at rest' position.
    Last edited by cfm; 09-02-2010 at 03:31 PM.

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    cfm
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    Quote Originally Posted by Rivernut View Post
    It sounds sort of like turbine whine, like a loud hiss.
    Yup - that's it ! Better description than mine.

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  6. #4
    Senior Member Rivernut's Avatar
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    Why do BG carbs do it but Holleys don't?

    Real Boats Don't Have Propellers!
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  7. #5
    cfm
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    They are not identical copies.

    Think of how when you whistle, you change shape of your mouth and the whistle changes tone. You can also change shape and make the whistle disappear.

    Anyhow, I have not investigated it further for the boats I have installed them on (small I/O's with small blocks) cruise just before the secondaries open with the light spring. If one want to go faster than this relatively fast cruise speed it is usually hammer down to WOT. So the noise is only heard for a second or two accelerating or decelrating.

    I'm assuming this noise is at your cruise speed and thus why bothering you ? Or is it not bothering you per say other than wondering if normal or not ?

  8. #6
    gn7
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    Some BG have an adjustable idle air bypass. Specially the larger ones for big blocks. It is adjustable by removing the air cleaner hold down bolt and going down thru the hole with a small screw driver. the bypass can and does whitsle. Thsi bypass is nothing more than an adjustable version of the ole hole drilled in the primary throttle blades.



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  9. #7
    Senior Member Rivernut's Avatar
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    I was curious if it was leaking somewhere. It's annoying too. Mine has the "idle-eaze" screw, but it is screwed closed as my engine makes plenty of vacuum. GN - you feelin' okay You left out any trash can references for the Grantster.
    Last edited by Rivernut; 09-02-2010 at 04:40 PM.

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  10. #8
    gn7
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    never really had one bad thing to say about the products ar their design/engeenering. QC is a little lacking sometimes, but even thats not the worst I've ever seen. It's their customers relations and product support that sucks. and it has come to bite him in the ass. Maybe he will change thing. Maybe not.



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