DIY: Fuel Petcock Rebuild - w/pictures
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Thread: DIY: Fuel Petcock Rebuild - w/pictures

  1. #1
    Join Date
    Apr 2014
    California, North L.A. county

    DIY: Fuel Petcock Rebuild - w/pictures

    DYI: Fuel Petcock Rebuild - w/pictures

    As our bikes have aged a bit, we may notice a small drip of gasoline or gas stain at the base of the fuel petcock. When these are first noticed, just switching the fuel petcock valve on and off a few times may temporarily "solve" the problem. The key word here is TEMPORARY, as sooner or later the drip, drip, drip will be back (or worse).

    The CX500TC (and others) are fitted with fuel petcocks that utilize a soft metal inserts which are mushroomed over the fuel selector dial plate to hold the assembly together. This method of assembly eliminates the added steps (and cost) of drilling, tapping, and screw insertion during the assembly process.

    In that the parts diagram of the fuel tank calls out the fuel petcock as an assembly, I ASSUME that HONDA never intended for this assembly to be rebuilt. The fact that there are no OFFICIAL replacement part numbers for the internal gaskets, X-rings, and the like should serve to confirm that assumption.

    Regardless of Honda's original intention - the fact that these parts are NLA necessitate that we rebuild our own petcocks from available parts. The process is quite simple and only requires an afternoons work, and I dare say that your finished product will be (much) better than new.

    Before you start:
    Before you begin you will need the following replacement parts:
    1 ea. Fuel Selector Gasket "Main Seal"- Honda p/n 16955-HA2-005
    1 ea. "X-Seal" - Honda p/n 16963-HB9-005
    Total cost was about $10.00 USD, and 4 days for delivery.
    -Thank you PIM205GTI for the part numbers -

    And the following tools, hardware, and shop aids:
    Drill motor
    Drill bit (see text)
    Tap (see text) & handle
    #800 carbide paper (or equivalent)
    razor blade
    metal polish
    yarn (or string / rag strip)
    Button Head Cap Screw (see text)
    Dental Pick (or equivalent)
    Degreasing solvent
    "OvenOff Oven Cleaner" (Sodium Hydroxide) - Safety Glasss + Rubber Gloves
    Jar for soaking

    Nomenclature and Parts Identification

    Begin -

    Empty the fuel tank and remove the fuel petcock (See section 4-15 of the shop manual). Being careful to NOT damage the plastic screen material of the "fill pipe/strainer".

    Remove the "fill pipe/strainer" (tan in color) by grasping the base of the pipe (end with no screen holes) and twist gently as you work the "fill pipe/strainer " free. Make sure you capture the black ring at the base of the pipe.

    Remove the "fuel return pipe" (white in color) by gently twisting as you work it free.

    Ready for rebuilding

    Set petcock into a padded vice
    File JUST the "mushroom" heads off of both of the soft metal inserts which holds the "fuel selector dial plate". The insert material is VERY SOFT and will yield to the file quite quickly - little effort is needed.

    -Alternate method: use a countersink bit to remove JUST the "mushroom" heads of the inserts -

    GENTLY pry the "fuel selector plate" from the valve body. Note the order in which the "wave spring", washer, and "fuel selector plate" are sequenced on the "fuel selector".

    Drill and Tap for your selected hardware size
    I chose 4-40 tap w/#43 drill - because it is correctly sized for the application (although NOT metric), AND, if I bung it up, I can re-drill and tap for M3 X .5 - always have a workable -thought out- "plan B" when your dealing with NLA parts. I also chose to use a 'button head cap screw" because the low profile of the button head (as opposed to the "socket head cap screw" ) negates the need to file the tip off the selector handle due to clearance issues.

    Note: As stated before - the insert material that is being tapped is VERY SOFT and will load up your tap quickly (2 turns or less). It is important that you use PLENTY of lubricant and back the tap out at the slightest hint of binding. Use a metal (brass) brush to clean the tap every time you back it out. Don't risk a broken tap - its not worth the time "saved".

    Valve Body and Selector clean-up:

    Degrease with your solvent of choice and inspect the valve body and selector .

    Inspection of the interior of the "valve body" and the "selector" will most likely show that both are contaminated with particulate debris and/or scale. The "selector" may have pits and/or machine marks across the face which mates to the gasket. Reassembly of the fuel petcock (with new gaskets) without addressing these issues is likely to result in premature failure (leaks). - Fortunately - it only takes a moment to refurbish this surface w/ #800 wet-or-dry carbide paper.

    AS REMOVED - Note the EXTREMELY POOR surface quality. Especially the rounded surface where the selector face mates to the gasket . This "selector" is eating up the gasket each time it is operated.

    AS REMOVED - Note the tan colored particulate which has "grown" (or bound itself to) the interior of the selector body. This substance was NOT removable by the liberal application of my favorite series of solvents - Acetone, Alcohol, and MethylEthylDeath (ref; USENET: Alt.Chem.Humor). If you have a clue as to what it might be ... let me know.

    A moment or two soak in - Sodium Hydroxide - aka "EasyOff Oven Cleaner" (SAFETY GLASSES - RUBBER GLOVES ... it says so ... RIGHT ON THE CAN) dissolved the 'barnacles" and the selector is ready for a few passes with the #800 carbide paper and a quick wipe with some metal polish.
    Note: The mold mark "2" is now clearly visible in the cleaned selector.

    While you have the #800 carbide paper out .... wrap a few turns of it around the drill bit that you used for the drill/tap operation. Lube the paper and (by hand) re-radius the "pass-thru ports" on the "selector".
    Then, set some wetted carbide paper on a smooth flat surface and pass the "selector" face over the paper in a figure "8" pattern. 20 (or so) figure "8's" should be plenty to remove most of the surface irregularities. A few moments using your favorite metal polish should produce a very nice surface finish.

    Using a straight edge and a razor blade - cut a strip of #800 carbide paper ( 6 to 10 inches long) to fit into the "x-ring" groove around the perimeter of the selector. Sand "shoeshine style" the bottom of the x-ring groove to remove any irregularities.

    Polish the bottom, and the sidewalls of the x-ring groove using wool yarn or string (or rag strip) and metal polish. Wipe polished surfaces and clean with your solvent of choice.

    Valve Body
    If you are fortunate, the "main seal" gasket can be removed by using just a dental pick (or similar) to lift out the seal - or parts of it. If you are not quite that fortunate (few of us are) I suggest an hour soak in "EasyOff Oven Cleaner " (SAFETY GLASSES - RUBBER GLOVES ... it says so ... RIGHT ON THE CAN) followed by a warm water rinse. ALWAYS RINSE YOUR PARTS WITH PLENTY OF WATER BEFORE HANDLING THEM.

    Repeat the -soak-rinse-inspect-pick- process until all of the gasket material is removed and the interior is free of debris.

    Wrap a fingertip with #800 carbide paper and refurbish the interior face of the valve body (interior mating surface for the x-ring). Finish up with metal polish to produce a good finish. Rinse with your solvent of choice.

    Install Gasket and X-Ring

    Gasket & Valve Body
    Remove the "main seal" gasket from the bag and align the 4 gasket holes over the 4 brass inserts in the "valve body". Press the gasket firmly into the "valve body" until it has bottomed out. Note: The gasket is symmetrical and does not have a front or back (as of this writing).

    X-ring & Selector
    Remove the x-ring from the package and place it IN the groove which runs around the circumference of the selector. Check that the x-ring is NOT twisted or otherwise deformed within the groove.

    Restack the "wave spring", washer, and "fuel selector plate" on the "selector" in the proper sequence.
    Align the "selector" and valve body and press the assemblies together. Be careful not to twist or pinch the x-ring. (It may be helpful to use a thumbnail to coax the x-ring into position within the valve body)

    Rotate the "selector" to the normal "ON" position with reference to the "valve body".
    Align the "fuel selector plate" to the "valve body" and the selector.

    Insert screws.

    Place the entire assembly in a suitable container of gasoline overnight. The "main seal" gasket and x-ring will swell and provide a leak tight fit.

    - I was QUITE dubious about this, until I did the experiment.-

    As seen in the following photograph - a "main seal" gasket which has been soaked overnight is compared (side by side) to one right out of the package. Results= +6% swell

    After soaking, remove the assembly and wipe dry.
    Carefully reinsert the (white) "fuel return pipe".
    Carefully reinsert the (tan) "fill pipe/strainer".
    Place the black ring over the "fill pipe/strainer" and slide it to the base of the valve assembly.

    Reinsert the assembly into the tank. (being careful not to damage the "fill pipe/strainer" during insertion)
    Orient the petcock and tighten the petcock locknut - securing the petcock to the tank.
    Set the petcock to the "OFF" position.

    Fill tank with one half gallon of gas and check for leaks.


  2. #2
    Senior Member
    Join Date
    Sep 2010
    N Va.

    you were not kidding, this was a pic heavy with good how I did it instructions. Thanks for posting this.

    Current 7 bikes:
    2012 Can Am Spyder RT-S (spring F/R changed, Corbin, windscreen w/ vent)
    2009 Aprillia SporCity 250 (suspension F/R, brake mods)
    1996 Honda PC800 (NT650V wheels/17" radial tires, CBR 600 F4 fork, rear shock change, F/R discs upgrades, Corbin, givi top case)
    1986 Honda VF700 (stock, to be sold)
    1984 Honda CB700SC (NT700V wheels/radials, VTR front fork/KYB rear shocks, F/R disc brake upgrades)
    1983 Honda GL650 (FJ1200 rear shock, modified comstars/radial tires and front suspension changes coming)
    1981 Honda CM400A (GL500I front fork, GL1100 front brakes coming)

  3. #3
    Senior Member Motomicah's Avatar
    Join Date
    Jun 2014
    Cambridge ON, Canada
    Never thought I'd need to clean mine out before.....really considering doing it now, and with this fantastic guide it should be easy. Thanks for the awesome tutorial!!

    • 1980 Honda CX500C
    "As I lay rubber down the street, I ask for traction I can keep, but if I spin and begin to slide, I pray that nothing happens to my sweet ride"

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  5. #4
    Senior Member hurley's Avatar
    Join Date
    Apr 2014
    Wallowa County, Oregon
    Wow, can we get this in the wiki?
    1979 CX500 Standard (finally riding!)

  6. #5
    Senior Member 81custom's Avatar
    Join Date
    Nov 2010
    I didn't see any picture of the black ring - you mention to be careful of.. Where does this bit come from - I don't think there was one on mine when I removed the petcock...

    and many thanks for the write up - it should go in the wiki - I still haven't put mine back together yet either......

    thanks again
    81 CX500 Custom

    82 CX500 Turbo

  7. #6
    Junior Member
    Join Date
    Jan 2015
    I´ve rebuilt my petcock with the help of this fantastic thread. But now I dont remember where to connect the two fuelhoses!
    Could someone help me? look at the picture I´ve taken.
    Name:  Petcock.jpg
Views: 3134
Size:  1.85 MB

  8. #7
    Member Panama Red's Avatar
    Join Date
    Aug 2010
    Grayson, GA

    Hose going to fuel filter goes to the gray barb and the hose to pressure regulator goes on the copper barb.
    79 Deluxe
    80 Custom
    82 Turbo (X2)
    74 Montesa Cota 247

  9. #8
    Junior Member
    Join Date
    Jan 2015
    Quote Originally Posted by Panama Red View Post

    Hose going to fuel filter goes to the gray barb and the hose to pressure regulator goes on the copper barb.
    Thank you Panama.

  10. #9
    Senior Member edinlr's Avatar
    Join Date
    Aug 2010
    Thanks again for this thread, I have five of these to do, so it sounds like a good assembly line project.
    CB750 w/turbo
    Kawasaki 750 Turbo
    Katana 1000
    Ducati 749R
    Screaming Eagle Road King
    Honda Metropolitan
    Ninja H2 1000
    & a dozen battery chargers

  11. #10
    Senior Member richnct's Avatar
    Join Date
    Aug 2010
    Connecticut, USA
    I would add an additional suggestion to your excellent writeup: Getting the very fine drill exactly centered for the two tappings is tricky, so I do not file off the staked pin, but use the dimple in it to center the tap drill and drill right on through. Then a larger drill or center drill to remove any remaining stake head. It seems that replacing the entire fuel tap with a new aftermarket non-vacuum one is more popular these days, for efficiency and simplicity, but where's the fun in that?
    Pim205GTI likes this.
    Sure, I'm crazy, but life is more interesting that way!

    '76 CB500T w/Velorex Hack

    '79 CX500C

    '82 GL500

    '83 GL650

    '83 GL650I

    '83 CX650 E,T (sold the C)

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