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Thread: Fuel Resistant Gasket Mat'l

  1. #1
    Join Date
    Jan 2002
    Location
    Huntsville Ala
    Posts
    4,951

    Default Fuel Resistant Gasket Mat'l

    The fuel mix cap (gasket) on my chainsaw was leaking. I'd filled it just a couple of weeks ago for about 5 minutes use, then today found about 2/3 tank of fuel in the bottom of the carrying case.

    Unfortunately it's bigger than any garden hose or other plumbing rubber washers I could find here around the farm.

    With some tedious use of a razor blade I made another gasket from an innertube. It has stopped the leak, but I'm concerned how that will hold up to the fuel. A little rubber shock absorber built into one of the handle attachments has turned noticeably gooey by the leaking fuel.

    I have some sheet cork that I could use. But wasn't sure that would seal the fuel, or permit it to ooze through.

    What say ye? Will the innertube mat'l hold up? Or would cork work better?

    Haven't checked, but my guess is the Stihl folks will only sell the gasket as a component on a new fuel tank cap. Not an expense ranking up there with a house mortgage, but still if I can fix this .... Plus, it's just more fun to fix things than to buy replacements.

  2. #2
    Join Date
    Jul 2007
    Posts
    1,431

    Default

    I vote for the sheet cork. It is actually intended for use around gasoline. The innertube, on the other hand will most probably swell up and go gooy.
    Duffy, Gatineau, Quebec

  3. #3
    Join Date
    Jan 2010
    Location
    Long Beach
    Posts
    367

    Default

    The inner tube will deteriorate and leak shortly. For gasket, use the cork material. I would try to find an O-ring of viton or anything that's not EPDM.

  4. #4
    Join Date
    Aug 2009
    Posts
    2,253

    Default

    I had the same problem with the gas cap on my string trimmer. It originlly had a special formed laytex seal that resembled the nipple on baby bottle. After 20 years it got kind of gummy and started leaking. I stamped out a gasket out of some rubber/cork type gasket material that worked OK for a short time but the gas swelled it and it failed to seal. The other problem is the cap has a small vent hole in the center of it and gas would leak out of it and run down my arm.
    Thats why the original gasket was designed like a baby bottle nipple. To keep the gas from splashing out of the hole.
    I finally made a small plug for the center of the cap out of the same gasket material I used for the main seal I pressed it in place, poked a few holes in it with a pin and it solved the gas down the arm problem. The seal swelled but it's still holding in place. I would look for some gas and oil resistant material like Buna-N. You can buy small square sheets from MC Master.

    JL...............

  5. #5
    Join Date
    Oct 2005
    Location
    British Columbia
    Posts
    3,443

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    The inner-tube material should be of a natural rubber composition and should start getting gooey. I'm surprised that the isolators are not standing up to the fuel/oil mix. I have several older Jonsereds and despite having chain oil and gas/mix on them they are as resilient as new.

    So yes the cork will last longer than the inner-tube. I often will insert an O-ring into a cap for these type of applications.
    Home
    Good judgment comes from experience, and experience....well that comes from poor judgment.

  6. #6

    Default Gasket Material

    Viton is the material you want. Various sizes of sheet material is available for the likes of Mc Master Carr.

  7. #7
    Join Date
    Jan 2002
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    Huntsville Ala
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    Default

    I have a collection of O-rings, but don't know what they're made of, so didn't really look to see if I had one the right size.

    I'll check an auto parts store the next time I'm by there and see what they have.

    In the meantime I'll try to keep an eye on the innertube seal, to see how it's holding up. I went ahead and made one of the cork/rubber sheet stuff I had. It's gasket material from Fel-Pro, but doesn't specifically mention gas suitable.

  8. #8
    Join Date
    Mar 2001
    Location
    South Florida and NC
    Posts
    1,175

    Default

    My comment doesn't exactly address your gasket material problem to the extent of suggesting a material, however I'd like to point out something else to consider in your choice of materials.

    Today's gasoline has methanol, up to 10%. This figure will possibly increase in the future as the government tweaks the regulations. I'll state up front that I'm not a methanol fan, however we live in a world where we have to deal with what comes our way. In this instance, methanol is harder on some materials than gasoline. I've had the rubber parts in my Shindiawa weed eater deteriorate in a matter of a few months since ethanol came into vogue whereas prior to methanol, the rubber parts lasted many years. I suggest cork as a possible solution but there are synthetics out there that can handle methanol very well.

    Since gaskets made of ethanol resistant materials aren't available for my Shindiawa and other lawn equipment I have started a regimen of mixing Marine Formula StaBil with the fuels I use for that equipment. In addition, since my Shindiawa seems more susceptible to ethanol issues I drain the fuel tank and run the carburetor dry between uses. That solution, in addition to using Tygon fuel lines has solved my problems for over two years now.

    The newer Flex Fuel vehicles have those materials incorporated into them to handle E85 (85% methanol). The materials are used anywhere that gaskets may come into contact with ethanol type fuels, including the oil filter gasket, as blow by will increase the fuel/ethanol concentrations in the crankcase as well as within the fuel system.

  9. #9
    Join Date
    Mar 2005
    Location
    Springfield Mo
    Posts
    28

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    Ethanol In Gasoline Problems


    Certain materials commonly used with gasoline may be incompatible with high-level ethanol blends, causing them to degrade and contaminate the fuel. Metals that have been shown to degrade over time in the presence of high-level alcohol blends include brass,(floats & jets) lead, zinc(carb bodies) and lead-based solder.

    Nonmetallic materials that degrade when in contact with ethanol include natural rubber, polyurethane, cork gasket material, leather, polyvinyl chloride (PVC) polyamides, and certain thermoplastic or thermoset polymers.

    On the other hand, unplated steel, nickel-plated steel, stainless steel, black iron and bronze have shown resistance to ethanol

  10. #10
    Join Date
    Aug 2009
    Posts
    2,253

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    The problem with using an O-ring is first off it may not stay in place or seal against the thin rim of the tank opening and second the cap may only grab by a thread or two depending on how many threads there are.

    JL..................

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