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Replacing Fuel Tap Corks (2016)

Discussion in 'Other Norton Motorcycles' started by texasSlick, Jun 13, 2016.

  1. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013
    Replacement corks are available for most fuel taps as found on our Brit Bikes. But they do not come with instructions on how to make the change. This is a DIY guide to replace the corks, and also a DIY guide how to make your own "better than new" substitute for corks. Note: this guide is typical for most fuel taps; yours may require some modifications.

    Step 1. Remove the spool assembly from the tap and make note of the orientation of the parts. It may look like one piece, but the part with the cork (I call that the spool) is pressed into the the part that has the lever or pull handle attachment (I call that the shaft). We will drive the spool and shaft apart, but before doing so, we will drill a 1/16 inch dia. hole thru the shaft and spool where indicated in the Fig below (the Figure already has the hole drilled).


    To facilitate drilling the 1/16 " hole, it is helpful to first make a drill fixture as shown in the next Figure. This is just a piece of flat stock into which we drill a hole to snuggly hold the shaft. A 1/16 " dia hole is drilled into the center of the hole for the shaft.


    Another look at the drill fixture with the spool and shaft inserted, and ready for drilling.


    Step 2. We are now ready to drive the spool and shaft apart. Insert a punch into the hole at the shaft end and drive the parts apart.

    Fuel Tap Disassembly.JPG

    Step 3. Remove the old cork. If you plan to replace the old cork with a new "store bought" one, slip it on, but be aware that I have never found a cork to be an exact "ready to go" fit. New corks invariably require sanding to fit, so go to Step 7 to continue.

    Step 4. Here I describe how to make a replacement cork plug that is better than store bought corks. Obtain a sheet of 1/16 " synthetic cork (available at most any auto parts supply). From this cork sheet, punch out about 8 discs using a 7/16 " dia. punch.


    Step 5. Using a leather punch, select a hole size to snuggly fit the spool shaft (for reference, my spool has a 5/32 " dia. shaft), and punch center holes in each of the discs. Don't worry about being on exact center as you will be sanding the discs concentric later.

    Step 6. Stack the discs on the spool. In the following Figure, I show only 4 discs for clarity, but it will take 7 or 8 to get a compressed stack. I also show an option, which is to use an O ring as the last unit in the stack. For my spool, a number 105 O ring fits the spool shaft, and fuel tap bore just right. Can't find the right O ring? Don't worry, the fuel tap will work fine with one extra cork disc in its place.


    Step 7. Insert the spool into the shaft (maintaining proper orientation) until the 1/16 " holes align in the spool and shaft, and with some compression on the stack. Insert a 1/16 " x 5/16" roll (spiral) pin, driving it in until under-flush on both sides of the shaft.

    Step 8. Chuck the spool assembly into a lathe or drill press and sand the stack, or store bought cork, until you get a snug sliding fit in the fuel tap bore.

    Step 9. Lubricate the spool assembly with bar soap. Do not use liquid detergent.

    The synthetic cork is less susceptible to drying out and shrinking, and is "tougher" than natural cork, making it less likely to get gouged by the action of moving past the orifice in the fuel tap. Then, there is the fact, that synthetic does not have any of the voids found in natural cork. These voids generally do not cause, or contribute to leaks, but the lack of such voids is some peace of mind.


    UPDATE: 30 Jul 2017
    I have used 1/16 " viton to make disks. Viton is rated impervious to ethanol. So far, no problems, and I like the "feel" of the viton disks when operating the tap more than cork.
    Last edited: Jun 24, 2018
  2. Rohan


    Aug 26, 2010
    Interesting. You sure this synthetic stuff is totally fuel resistant, long term ?
    Including ethanol and all the recent type fuel additives.

    If the natural corks are well boiled up (in boiling water) for a while before installing,
    they are less liable to dry out in use.
    Also seems to make them tougher.

    If you are stranded in the desert you may also be able to eat them,
    although after being in contact with the fuel may not taste so good !
    Or nutritious....
  3. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013

    When it comes to ethanol, I am certain of nothing! I experimented with different materials for the discs. For example, vinyl according to material compatibility charts was rated A+ for gasoline, and A for ethanol, but after 3 weeks soak in non ethanol gas, shrunk and became hard and brittle. Silicone is impervious to fuel, but I found it to be too soft, and it was gouged passing the orifice. Teflon would likely make an ideal plug, but being hard, would require a better machinist than me, or most DIY'ers to make it work.

    The synthetic cork comes with "suitable for automotive use with fuel, oil, and water" claims, for what that is worth. I have had the synthetic cork on my fuel tap for about 6 months now with no ill effects. I have read of others who made synthetic corks from wine corks, by cutting a plug and drilling the center hole. I tried this with some success, but whenever one cuts a plug from a thick material, one gets an "hour glass" shaped cylinder. This is of little concern, as the plug must be sanded to size, but the cutting also gouges voids.

    Prior to using synthetic cork, I would boil my corks, but I found this did not make them shrink proof. I cannot say if it made them tougher. It seemed to me, boiling just swelled the cork back if it had shrunk. One other point regarding natural cork, I found it had a tendency to stick in the bore from non-use. I nearly ruined a fuel tap, trying to "unstick" one.

    Anyone who is suspect of synthetic, can use store bought corks. Half the point of the post was a "How to do it" replacement method.

  4. J. M. Leadbeater

    J. M. Leadbeater

    Apr 21, 2015
    Thank the gods I have always used solid brass taps!!
    marinatlas likes this.
  5. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013
    UPDATE to the original post - Mar. 5, 2019.

    I have found the Viton disks failed due to the internal orifice gauging out bits of the Viton as the stem moved across the orifice.


    There is a leakage path along the stem of the spool to the push/pull shaft. If the hole in the disks is a snug fit on the spool shaft, the leak path is sealed. Otherwise, fuel may leak from the drilled hole with the roll pin, and from the end of the push/pull shaft.

    I sealed both points with solder. Perhaps, blue Loctite might be adequate as a seal, but I worried ethanol might deteriorate Loctite.


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