1997 blackbird horrible mpg
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  1. #1

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    1997 blackbird horrible mpg

    Hi guys. I've been getting under 30mpg on my bird, even as low as 24mpg. As it's a carb there is no FPR as far as I'm aware? I've changed the plugs but no difference. It has a full stainless exhaust. The temperature gauge always stays down on the cold mark even on long runs, it will only rise when sitting in traffic.
    Does anyone know what could be wrong? It's getting annoying goin for a spin and consistently filling up!

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  3. #2

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    Re: 1997 blackbird horrible mpg

    I had shocking MPG with a carb bird on full Remus exhaust. It popped a lot on engine braking. I would gte maybe 90 miles to a tank.

  4. #3

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    Re: 1997 blackbird horrible mpg

    Did it return better in the past or has it always been bad? What colour were the plugs when u changed them? If high milage, may be carb refurb time or choke sticking on.I assume there's no smell of fuel leaking?
    The answer is 42

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  6. #4

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    Re: 1997 blackbird horrible mpg

    Yeah that really is bad, mine usually gets ~13L/Km or ~30Mpg but will drop to ~11.4L/Km or ~26.8Mpg
    Mine would originally get ~15.4L/Km or 36.2Mpg when I got it so I'm guessing the carbs have worn over time
    98 TITANIUM Blackbird
    OzBB.net Administrator

  7. #5

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    Quote Originally Posted by Krisbiker2 View Post
    Did it return better in the past or has it always been bad? What colour were the plugs when u changed them? If high milage, may be carb refurb time or choke sticking on.I assume there's no smell of fuel leaking?
    Plugs were ok looking when I changed them, a dark brown, there is 40k miles on it

  8. #6

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    Re: 1997 blackbird horrible mpg

    At 40k, would expect carbs to be ok, could be choke issue or maybe fuel tap leak into vaccuum tube? I'm too long away from carbs for any other suggestions, hopefully someone else maybe able to help? I do notice your sig says 2001 Bird tho, that is FI times? Also- you say stays in cold on gauge, from memory carbs do run colder than FI but would expect a bit higher so maybe not getting up to temp? Also, may not be fuel related- something silly like brakes binding?
    Last edited by Krisbiker2; 07-29-2018 at 6:33 PM.
    The answer is 42

  9. #7

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    Re: 1997 blackbird horrible mpg

    You want the plugs a light tan color to possible grey. Check the vaccum shut off valve at the bottom of the tank. It can start to fail and allow the system to draw fuel in through there causing a drop in mileage and rich run condition your seeing. The other possible culprit could be leaking needle seats in the carbs. Even at 10% ethanol it can raise cain with fuel system parts. a quick and dirty trick is to take a piece of clear fuel line about 12 inches and slip it onto the drain valve port on the bottom of the carb. With the bike setting on the center stand and running. Take open end of the line and hold it up. Leave a decent drop loop in the line and with the bike running open the drain screw. The fuel will fill the bend and should come up level with the parting line between the carb body and the bowl if the fuel level is correct.
    Last edited by beestoys; 05-10-2019 at 1:49 PM.
    Route 191 formerly Route 666 Some say that this section of the
    road has 1100 curves in 95 miles.

  10. #8
    Supercharged Mod
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    Re: 1997 blackbird horrible mpg

    Quote Originally Posted by Maddi680 View Post
    Plugs were ok looking when I changed them, a dark brown, there is 40k miles on it
    Dark brown sounds a tad rich to me, 'light tan' is what you should be expecting (what I always used to look for when I checked any carb motor). I'm not a Bird Carb man so I won't make suggestions …..
    Full of Hot air? Intercool yourself............ you know it makes sense

  11. #9

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    I reckon it's running rich alright as you can smell the fuel when running. I had a 01 bird and changing the FPR sorted the fuel issue on that but on the carb version I'm not sure what to do?

  12. #10

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    Re: 1997 blackbird horrible mpg

    If the thermostat is stuck open, your mpg's can suffer. Motor runs too cool.

  13. #11

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    Re: 1997 blackbird horrible mpg

    Quote Originally Posted by Maddi680 View Post
    I reckon it's running rich alright as you can smell the fuel when running. I had a 01 bird and changing the FPR sorted the fuel issue on that but on the carb version I'm not sure what to do?
    See bees answer above for starters
    The answer is 42

  14. #12
    BirdDog
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    I know it’s sounds crazy but many years ago I ran a K&N air filter (for about a week) on my 97 carbie with two bros slip-ons and not only did it run too rich, fuel mileage suffered dramatically (30mpg on a good day). I went right back to the OEM FILTER. I avg 38 mpg cruising 90mph on long highway hauls I can get as high as 43mpg depending on temperature, barometric pressure and humidity taken into account as variables. But again, 38mpg is pretty consistent for me on avg.

    My dog always pee’s on my wheels before a trip...why is that?

  15. #13

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    Re: 1997 blackbird horrible mpg

    Second the airfilter causing issues as well. But I'd check float levels. There used to be a pdf of the factory manual in the resources section. It might detail the clear line check I described. If the float levels look goos then you could have picked up debris in the fuel circuts. Best start with the vacuum port first on the petcock. It should be fuel free if not then that hqs has to be fixed first.
    Let us know what you find and we can go from there.
    Route 191 formerly Route 666 Some say that this section of the
    road has 1100 curves in 95 miles.

  16. #14

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    Re: 1997 blackbird horrible mpg

    Hi. A bit of thread hijacking here... I wonder how or if this issue was fixed? O.P. hasn't followed up here, so I'm curious how this went down since I maybe have a similar issue with my 1998 BB. It's not that extreme in the fuel consumption, but still not very good, and smells a bit too much of gas from the right exhaust while riding. I have'nt been able to check the sparkplugs yet.
    Thinking of hooking up a clear fuel pipe to the drain on the carbs as beestoys said to check if the floater valve is stuck. Since this is easyer than getting the sparkplugs out... Is there anything more to think of with this kind of issue?
    (There is not any fuel in my vacuum tube to the petcock.)
    Edit: I thought that I should smell the motor oil again today, I've done that a while ago and it was not smelly. So, I opened the oil fill cap and smelled it. Of course it was smelling of petrol/gas!
    So, to clear out my different things to check and in what order:
    1. Check floater valves as beestoys advised
    2. Check sparkplugs condition and function
    3. Check vacuum valve in the petcock
    4. Should I check thermostat or is that not needed on a carbed bike since it has manual choke?
    Last edited by stellborn; 05-10-2019 at 1:27 PM. Reason: Update due to new info

  17. #15

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    Re: 1997 blackbird horrible mpg

    Stell
    It depends on the results if the 1st 3 checks. Let us know what you find.
    Route 191 formerly Route 666 Some say that this section of the
    road has 1100 curves in 95 miles.


 
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