Could someone explain fuel line sizing and sourcing for Hondas?
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Thread: Could someone explain fuel line sizing and sourcing for Hondas?

  1. #1
    Member saganaga's Avatar
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    Oct 2018

    Could someone explain fuel line sizing and sourcing for Hondas?

    One of my carbs is missing the overflow drain tube that directs extra gas to the pavement instead of letting extra gas pour onto the hot bottom end of the engine.

    I'd like to replace it - but the lines goes through a small clip that holds the overflow lines from both carbs as well as some drains from the air box. A regular (designed for pressurized gas from a fuel pump) fuel line is too large. The fitting on the bottom of the carb seems to have about a 5mm diameter. So I'd assume a 5mm (or perhaps 3/16") ID fuel line (not designed for fuel injection) would work.

    Is this correct?

    Where is this usually sourced?

  2. #2
    Senior Member budlite282's Avatar
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    Nov 2012
    You can also use vacuum hose designed for a car.

    Only use it as overflow though, not for fuel supply line.

    I actually used the hose that came with those sprinkler systems you buy at Lowes.

    Those small 22 bux systems.
    "If it ain't raining, I'm riding......"

    Work in process:::::::

  3. #3
    Senior Member ancientdad's Avatar
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    Nov 2016
    Nature Coast FL
    7,957 has OEM-sized Honda fuel line you can use for both drain tubes and fuel hose, 3.5mm and 5.5mm
    76TWIN likes this.

    Ride along at the drag strip -

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  5. #4
    Senior Member dtsmjr8dan's Avatar
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    Oct 2011
    Windsor, Ontario, Canada
    Small engine repair shop should have fuel line for chainsaw/etc. Thin and fuel resistant at the same time.
    1979 CM400T (rider),
    1979 CM400T (resting)
    1980 CM400T (just picked up in pieces)
    1981 CM400T (in surgery receiving transplant)
    1982 CM450 (donor engine for 81)
    1982 CB450 (parts bike)
    1985 VT1100C (rider)

    Past rides: Vincents, Triumph, BSA's, Suzuki's, Twingle, Corgy, others.

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  6. #5
    Member saganaga's Avatar
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    Oct 2018
    Looks like the 3.5mm line was used as a drain line. Thanks everyone!

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