Need some help and advice......

Discussion in 'Motorized Bicycle General Discussion' started by donutguy, Feb 28, 2010.

  1. donutguy

    donutguy New Member

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    Hi all, what I'd like to do is get fuel from an upper tank to a lower tank. I have a 2.5 liter tank, fuel line and petcock on order.

    Here is a pic of how the bike is now...

    I will be mounting to tank to the top tube and would like ideas on how I can get the fuel from the top tank to the lower tank.

    I realize I could just run enough fuel line to the rear tank and leave it there until I need fuel-open the rear tank and put line from upper tank in the opening and open the upper tanks petcock until the lower tank is full. Not a very glamorous solution.

    Does anyone have a better solution? If I could somehow put some sort of fitting on the lower gas tanks cap...would that work?

    I know there are lots of smart guys on this board......I'd be more then happy to hear your ideas or if someone sells something I can buy-point me in the right direction.

    Why so much fuel? I am going to be commuting on the bike when it gets warmer and I need enough fuel to go 50 to 60 miles with plenty in reserve in case I do a ride right after work.

    Thanks all-George
     
  2. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    If your bottom tank isn't completely seal, it won't work. make sure any fittings are leak proof, or all the gas will run to the lower tank and out any minute leaks.
    Or, use the top as a reserve only, and turn on the petcock until the bottom tank is filled, then shut it off again.
     
  3. Cannonfish

    Cannonfish New Member

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    Just a thought - I don't know the specifics of your carb's fuel intake, but you could buy a motorcycle or moped gas tank off ebay (or craigslist etc) and mount it on your top tube (in front of your seat).

    This would give you plenty of fuel capacity, and allow you to completely do away with the tiny gas tank you currently have. From the picture you posted, it looks like a top-tube-mounted gastank would be higher than the level of your current tank, so flow wouldn't be an issue.

    Motorized bicycles tend to get somewhere between 90 to 150 mpg, so if you're commuting 60 miles roundtrip, then you could use something in excess of a gallon capacity just to be on the safe side.
     
  4. donutguy

    donutguy New Member

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    Yeah, my bottom tank is one piece-only opening is the fuel cap.

    I am looking for a way to link the top tank to the bottom tank so I don't have to manually use the top fuel tank as a reserve that I have to stop to manually fill the lower tank.
     
  5. kbot6789

    kbot6789 New Member

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    heres an idea drill a hole in the side of the tank the plastic tank then mount your tank on your bar like you want run the fuel hose through that hole you drilled then when you need more gas just open the valve till the tank is full then shut the valve but use to kinda sealant whare the tube goes in the lower plastic tank
     
  6. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Make a fluid tight fitting for the cap and you'll be golden. Make sure you have a vet in the top tanks cap.
     
  7. corgi1

    corgi1 New Member

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    I would use the top as a reserve and turn it on to top off the bottom tank when stopping to rest simple turn it on ,fill turn it off..the tank on the engine will take you 35?45?55?miles?,,,Thats a long time to be sitting on a bike seat ,on matter how comfortable it is and traveling at a steady speed of 30 mph it is 2 long hours to go 60 miles wow I'm tired just thinking and typing(2 finger hunt and peck)lol
     
  8. donutguy

    donutguy New Member

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    Hey corgi1....before I had arthritis so bad in my knees- I used to ride 60 to 70 miles at a clip *without* a motor.

    I have callouses where the sun don't shine:)
     
  9. Nougat

    Nougat New Member

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    Your lower tank fuel cap is surely vented. If you allow a top tank to freely flow into the lower tank, it'll overflow out of the lower tank cap vent.

    If you wanted to have a continuous flow, you'd need to have a non-vented cap on the lower tank, a vented cap on the upper, and the tube between the two always open. Even so, you might have flow problems from the upper tank to the lower unless you had a vent tube from the lower tank to the top of the upper tank.

    Edit: Of course, if you only use the top as a reserve, and keep the vented cap on the bottom, then you'd only have to worry about the one tube. Just close the petcock between the two before the lower tank overfills.
     
    #9 Nougat, Feb 28, 2010
    Last edited: Feb 28, 2010
  10. donutguy

    donutguy New Member

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    Actually, my lower gas tank has a non-vented gas cap- their are two lines running from the carb down to the tank-I would assume the second line is a return line or a vent line.
     
  11. Nougat

    Nougat New Member

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    Huh, yeah, one of those lines is a vent line, then.

    If the existing tank is below the carb now, I wonder whether having additional fuel pressure from gravity (from a top tank) would cause a flooding problem. I'm not sure how the fuel from the lower tank gets drawn up to the carb on that setup.

    Edit: Oh, I know what would happen - if you leave the petcock from the top tank open long enough, fuel will start coming out of the vent tube in the carb. I think you definitely want to use a top tank as a "hot reserve," but not leave the valve between the two open.
     
    #11 Nougat, Feb 28, 2010
    Last edited: Feb 28, 2010
  12. donutguy

    donutguy New Member

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    Nougat....that's what i am thinking as well. A hot reserve might be the way to go.

    I'm looking at drilling a hole in the lower gas tank's cap and inserting the fuel line from the upper tank and filling the lower tank as needed.

    Just have to make sure I have the line going into the lower gas cap sealed properly.

    I think there are a variety of sealants out there I can use to bond the fuel line to the lower gas cap.

    Once I get all the parts, I'll let ya'll know how it ends up and I'll post up a picture of my final set-up

    This stuff sure is fun and you guys have lots of great ideas!

    Thanks much-George
     
  13. 2door

    2door Moderator
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    George,
    Your carb is a diaphram type that 'sucks'. The two lines are for fuel and vent. The same system is used in the new Titan, (HS) 35cc motors. The tank cap is non vented. I would probably go with Bike Guy Joe's advice; run a fuel line down from the upper tank with a petcock between it and the lower. Use the upper as your reserve but remember you'll need to vent the upper tank so fuel will flow when you open the petcock. Retain the non vented cap on your lower tank to prevent overfilling and leakage.
    Tom
     

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