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  1. #1
    spud's Avatar
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    Pressure in gas tank

    I have been thinking about putting a stem on my gas cap and using a pump and a low pressure gage and pumping it up to 2 or 3 psi before doing runs.

    Anybody have any feedback?

    Thanks


  2. #2

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    Cool

    your trying too hard

    later cd

  3. #3
    ....back from the dead.... J-ME's Avatar
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    If I remember correctly, Island Racing does the opposite.

    They remove the check valve completely so there are no pressure variations (other than atmopheric) to complicate tuning. (Eg. sun heating or agitation)

    As long as you keep the pressure the same, I don't see any problems.

    It would be cool to have a blow off for the tank like the dirt circle track guys use on their tires to maintain pressure during a race; BUT fuel vapors are nasty stuff !

  4. #4
    MR. SCOVILLE UNIT SUCKMYWAKE's Avatar
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    blah blah blah yada yada

  5. #5
    spud's Avatar
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    I noticed my rpms falling off on my project ski. After I filled it to 1/2 tank problem gone. The ski will run down to the fumes and the tank does pressurize. When I removed the cap there was no pressure at all it was so cold. The tank does have a popoff valve so it won't over pressurize.

    Worst case it doesn't do anything no big deal. Its winter, its time to think.

    I am using an old stock gas cap so no loss.

  6. #6

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    Cool

    The snowmobile guys (who have carb’s) run an external vent for the diaphragms on the carbs (if you think about it they see ambient pressure if not getting enough air into engine compartment, well that diaphragm not going to move much (that info came from the Decker brothers)

    Later cd

  7. #7
    spud's Avatar
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    I was talking to Lowell yesterday. He told me snowmobiles have carbs similar to dirt bikes. Jet Skis carbs cannot be vented so they are a strange breed in the carb department. My dirt toys all had three or four vent tubes on them.

    I'm just talking about an initial pressurization similar to what a little riding and heat will provide so the first run on is good.

    In warmer weather this isn't even a concern.

  8. #8
    Hydrotoys's Avatar
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    Spud,

    Go to autozone, and get another checkvalve. Coming off your gas tank, run a tee. On one side of the tee run the check valve one way, and on the other side run the check valve the other way. This will maintain a constant pressure, under all conditions.

  9. #9

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    Cool

    I think thats how seadoo does it

    later cd

  10. #10
    Moderator RX951's Avatar
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    Quote Originally Posted by chip View Post
    I think thats how seadoo does it

    later cd
    It is



    Bombardier FUEL SYSTEM Diagram

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