Gas Valves (Petcocks)

Gas Valves listed by Type

Here 53 gas valves (petcocks) are listed by size and type.
Click on the part number to see photos, info and price.
All valves use 3/16″ (5mm) I.D. fuel hose, unless noted.

part#  thread  Screw-on Gas Valves
0A1  08-1.00 male spigot L or R push-pull
0A2  10-1.00 male spigot down

0A3  10-1.00 male spigot back
0A4  10-1.00 male spigot left
0A5  10-1.00 male spigot right
0A6  10-1.00 male spig. back medium shaft
0A7010-1.00 male spig. down 15 extender
0A8  10-1.00 male spig. down 20 extender
A8b  10-1.00 male spigot left  20 extender
A8c  10-1.00 male spig. right  20 extender
0A9  10-1.00 male spig. down 26 extender
A10  10-1.00 male spigot left  26 extender
A11  10-1.25 male spigot right
A12  12-1.00 male spigot down
A13  12-1.25 male spigot down
A13b12-1.25 male spigot left
A14  12-1.00 female spigot down
A15  12-1.00 female spigot back
A16  12-1.00 female spigot back clear trap
A17  12-1.00 female spigot left
2-1.00 female spig left ext. round knob
A18  12-1.00 female spigot right
A19  12-1.00 female spigot back short shaft
A20  12-1.00 female spig. left medium shaft
A21  12-1.00 female sp. right medium shaft
A22  12-1.00 female spigot right  long shaft
A23  12-1.00 female side mount Ciao
A24  12-1.00 female side mount Puch
A25  14-1.00 female spigot down
A26  14-1.00 female spigot left short reserve
A26b14-1.00 female spigot left
A27  14-1.00 female spigot right 1/4″ hose
A28  14-1.00 female spigot back
A29  14-1.00 female side mount Trac
A30  14-1.25 male spigot down 1/4″ hose
A31  16-1.00 female spigot down
A31b16-1.00 female spigot down detachable shaft
A32  16-1.00 female spigot back
A33  16-1.00 female side mount KTM
A34  16-1.00 female spigot back
A35  16-1.50 female side mount Indian
A36  16-1.50 female spigot right
A37  16-1.50 female spigot down
A38  22-1.00 female spigot down
A39  22-1.00 female sp. down medium shaft
A40  14-1.00 vacuum-automatic
A41  16-1.50 vacuum-automatic
part#  Clamp-on, Bolt-on, Remote Valves
13mm clamp-on spigot right
0B2  15mm clamp-on spigot down 1/4″ hose
0B5  12mm clamp-on spigot back
0B6  12mm clamp-on spigot right
0B7  12mm clamp-on spigot down
B13  bolt-on petcock side mount Angel
B15  remote petcock (in-line) Trac
B16  remote petcock (in-line) Suzuki


Gas Valves listed by Application

Here are 177 applications (what bikes take what valves).
Click on the part number to see photos, info and price.
These are US models (sold new in the USA), unless noted.

orig.  use
A15  A15 1980-82 AMF Roadmaster 130
0A8  0A8 1980-83 AMF Roadmaster 140, 141
A28  A26 1978-84 AMS (Her Chee) Sierra 50, Tahoe 50
A13  A13 1978-80 Angel (TYM) BP48, BP48-S (tube frame)
B13  B13 1977-78 Angel (TYM) AP48 (sheet metal frame)
0A8  0A2 1978-80 Arciero (Italtelai) Eagle, Hawk, Sea Gull
A00  0A4 
1978-80 Arciero (Italtelai) top tank
A17  A17 1999-02 Avanti (Mont) Kobra, Mont, Autopower
A17  A17 
1999-02 Avanti (Mont) Super Sport, Cosmo Stinger
orig.  use
A3  0A3
1977-80 Baretta (Piccoli) Magnum, also A4 or A2
0A3  0A3 1977-79 Baretta (Piccoli) 22, 38 (regular tube frame)
A21  A21 
1977-80 Baretta (Piccoli) 44, 45 (large mono-tube frame)
A14  A14 
1976-78 Batavus VA (step thru)
A15  A15 
1977-80 Batavus HS50, Starflite, Regency
0A2  0A2 1969-73 Benelli Buzzer, Hornet, Woodsbike, also A4
0A2  0A2 1967-77 Benelli Dynamo, Compact, Hurricane, also A4
A0 0 A20 
1976-80 Benelli (SEIMM) G2, C2 (mono-tube frame)
A18  A18 1976-79 Bermuda (Flandria) vertical type mounted sideways
A37b A31b ’77-79 BETA L, SL, SL-5 
0A8  0A2 1977-80 Bianchi (Italtelai) Stardust (step-thru)
A00  0A4 1978-80 Bianchi (Italtelai) Satellite (top tank)
0A4  0A4 1976-80 Bianchi (Italtelai) Snark (step-thru)
A00  0A3 1971-73 Broncco (Fantic) Diablo
orig.  use
0A2  0A2 1977-79 Carabela (Acer-Mex) Motomatic
A14  A14 1977-80 Casal K196 (top tank)
0A4  0A4 1976-77 Cimatti Twin Sport (dual tanks, front tank)

A17  A17 1977-78 Cimatti Town Bike (single front tank)
A17  A17 1978-79 Cimatti Twin Sport (single front tank)
A18  A18 1976-79 Cimatti City Bike (with original 10-12 adapter)
0A2  0A2 1976-79 Cimatti City Bike (no adapter, difficult to install)
A28  A26 1978-80 Clinton (Jui Li) ST (step-thru) (also A28)

A17  A17 1979-80 Columbia Commuter, Open Road (mono tube frame)
A18  A18 1976-80 Columbia Commuter, Open Road (sheet fr.) also A15
A18  A18 1978-80 Columbia Imperial, Western Flyer, Yard Man (sheet)
A18  A18 1980-81 Columbia Medallion, Western Flyer Apache 3000 (t.t.)

0A2  0A2 1977-79 Concord (Fantic) XKE (mono-tube frame)
0A2  0A2 1979-80 Concord (Fantic) Freedom, Invader (can be 10 or 12)
A14  A14 1979-80 Concord (Fantic) Freedom, Invader (can be 10 or 12)
0A3  0A3 1977-79 Cosmo (Piccoli) Blazer 1, 2 (step thru)

0A3  0A3 1978-79 Cosmo (Piccoli) Colt 1, 2, 5 (top tank) also A4 or A2
0A3  0A3 1979-80 Cosmo (Malaguti) Colt 3,3A,4,4B (top tank) also A4, A2
A00  A00 1980-80 Cosmo (Testi) Amico (step thru enclosed body)

A17  A17 1999-02 Cosmo (Mont) Stinger, Avanti Supersport (top tank)
orig.  use

0A3  0A3 1976-79
DEMM Smily, Scout, also A4
0B2  0B2 1976-89 Derbi Variant SL, Variant SLE, TT, Variant Sport
A30  A30 1978-86 Derbi C5, RD50, Sport Laguna (top tanks)
0A4  0A4 1974-79 Di Blasi R2 folding mini-cycle (on right side)
0A5  0A5 1979-97 Di Blasi R7 folding mini-cycle (on left side)
0B5  0B5 1997-00 Di Blasi R7E folding mini-cycle (on left side)
0B6  0B6 2000-on Di Blasi R7E-V2 folding mini-cycle (on left)
orig.  use

A18  A18 1982-82 Eagle (Hercules) I, II (step thru) also A15
A18  A18 1982-82 Eagle (Hercules) III (top tank) also A15
orig.  use

0A3  0A3 
1977-79 F. Morini (Lem) Chembol, also A4
A32  A32 1977-79 Flying Dutchman (Kynast) (tube frame)
A32  A32 1976-77 Flying Dutchman (Sparta) (sheet frame rear tank)
A31  A31 1977-80 Flying Dutchman (Sparta) (sheet frame front tank)
A33  A34 1977-80 Foxi (KTM) Deluxe, Baron, Salzburg 

A31  A31 1977-80 Foxi (Sparta) GT, GT Sport, Flying Dutchman
A28  A26 1979-80 Foxi (Jui Li) 47 (top tank) also A25
0A3  0A3 1977-78 Foxi (Testi) Silver Foxi (mono-tube) also A2
orig.  use
0A5  0A5 1977-80 Gadabout (Moto BM) also A3
A15  A15 1973-78 Garelli Eureka, Sport, Gran Sport, Gulp
A15  A15 1978-80 Garelli Sport, Rally Sport also A17
A17  A17 1978-80 Garelli VIP 

A15  A16 1978-86 Garelli Super Sport XL, LTD, SSXL 
A15  A21 1984-85 Garelli Basic (needs long reserve tube) 
A19  A19 1980-86 Garelli Sport, Rally Sport, Rally SL
A15  A15 1983-86 Garelli Monza GT
A32  A32 1970-73 Gemini SST 80 mini trail

A28  A26 1979-85 General (Jui Li) 5-Star (top tank) also A25
A28  A26 1979-85 General (Jui Li) 5-Star ST (step-thru) also A28
0A3  0A3 1984-86 General (Moto Meteora) TE (step thru)

0A3  0A3 1977-80 Gitane (Testi) OKS, Sport (tube frame) also A4 or A2
0A3  0A3 1977-80 Gitane (Testi) CL200 Confort (sheet frame) also A4, A2
0A3  0A3 1977-80 Gitane (Testi) Cricket, Super Sport (mono-tube) also A2

A28  A26 1978-80 Grycner (Jui Li) and re-brands
orig.  use

0A2 0A2 1965-66 Harley Davidson M50 
A15  A16 90’s-00s Hero (Majestic) Pacer, Panther also A17
A17  A17 90’s-00s Hero (Majestic) Gizmo
A25  A25 1979-81 Honda NA50 Express II
A26  A26 1977-83 Honda NC50 Express
A36  A36 1982-83 Honda NC50I Express Iowa
A40  A40 1981-82 Honda NX50 Express SR  16950-187-671
A27  A27 1982-82 Honda MB5 (MB50)
A37  A37 1968-78 Honda Z50 Mini Trail, QA50, MR50
A16  A16 1977-83 Honda PA50 Hobbit
A18  A18 1966-75 Honda P50, PC50 Little Honda
orig.  use

A35  A36 1979-83 Indian (Merida/Mira) AMI-50 
A24  A24 1976-78 Intramotor-Gloria Blanco (sheet frame)
0A3  0A3 1976-79 Intramotor-Gloria Scout also A4 or A2
0A5  0A5 1976-76 Itom Automatic
orig.  use
A38  A38 1970-82 Jawa Babetta 28, 206, 207
A32  A32 1980-83 Jawa Supreme, Supreme II (top tank)
A32  A32 1984-90 Jawa 210 Sport, Alley Cat (top tank)

A15  A18 1978-79 JC Penney (Kromag) Pinto, Swinger
A28  A26 1978-80 Jui Li Honey 50 and compatibles
orig.  use
A14  A14 1995-05 Kinetic TFR, TFR-USA also A16
A18  A18 1987-93 KKM (Columbia remake) Mopet
A39  A39 1995-99 Korado (Manet) (mono tube frame)
A00  A14 1977-80 Kreidler Flory MP9, MP19 also A18

A33  A34 1977-80 KTM Foxi Deluxe, Baron, Salzburg
orig.  use
A28  A26 1977-80 Lazer (Jui Li) Sport 50, Sport 50 ST
A28  A26 2009-on Lazer (Bashan) SSR Lazer 5 (step thru)
orig.  use
0A3  0A2 1976-79 Maico (Moto Bimm) MPI also A3
0A3  0A3 1977-80 Malaguti Commuter (step thru) also A4

0A4  0A4 1978-79 Malaguti Pilot (top tank)
A28  A26 1979-80 Moprix (Pou Yen) Speed Bird (step thru)

A27  A25 1979-80 Moprix (Pou Yen) Moprix (top tank)
0A1  0A1 50’s-60s Motobecane/Motoconfort
0A2  0A2 1978-79 Motobecane Model 7

0A4  0A4 1971-80 Motobecane 40, 50, 50V, Moby, Traveler, Le Moped
A15  A15 1980-81 Motobecane Sebring (Italian top tank)
0A3  0A3 1977-79 Motobee (Testi) RS100 (step thru) also A4
0A3  0A3 1977-79 Motobimm (Bimotor) (step thru) 

A15  A15 1971-80 Moto Guzzi (SEIMM) Chiu, Robin (sheet frame)
A00  A20 1977-80 Moto Guzzi (SEIMM) Robin (mono tube frame)
A15  A15 1985-90 Motomarina (Moto Meteora) Sebring (top tank)
0A3  0A3 1987-89 Motomarina (Moto Meteora) Raven (step thru)
0A3  0A3 1987-89 Motomarina (Moto Meteora) Tri-Power (3-wheeler)

0A2  0A2 1978-79 Motron Sprint, Medalist, Classic also A3, A5
0A8  0A2 1980-81 Motron Medalist, Classic also A3, A5
A14  A14 1979-82 Murray (all models) (step thru) also A17
orig.  use
A3  0A3 1977-82 Negrini Harvard, Harvard II (step thru mono tube) also A4
0A3  0A3 1977-82 Negrini Leprotto, Gazelle, Gazelle II, III (step thru) also A4
0A2  0A3 1977-82 Negrini MX Sport, MX Sport II (top tank) also A3, A4
A00  0A6 1976-78 NVT Easy Rider ER, ER2, Scorpion (mono tube)
orig.  use
A27 A26a1978-80 Oakwood (Pou Yen) Catalina
A00  A32 1977-80 Odyssey (Solo) 32/1, 40/1, 40/2 (step thru)
orig.  use
0A7  0A2 1978-80 Pacer (Italtelai) Deluxe P14 (step-thru)
0A8  0A5 1978-80 Pacer (Italtelai) Sport P78 (mono-tube) also A4

0A0  0A4 1979-80 Pacer (Italtelai) Super Sport (top tank)
A8c   A8c 1980-80 Peugeot 102SP also A8
0A2  0A2 1976-83 Peugeot 103, 103SP, TSM
A12  A12 80’s-90s Peugeot Vogue (Euro model)
A32  A32 1978-86 Puch Magnum XK, MkII, II, Cobra 1, 2 (top tanks)
A24  A24 1969-86 Puch Maxi, Sport, Newport models (sheet frame)
A31  A31 1954-68 Puch MS50, VS50, VS50D (Euro models) (sheet frame)
A39  A39 1995-99 Puch (Manet) Korado (mono tube frame)
A24  A24 1989-92 Puch (Piaggio) Super Maxi (Euro model)
orig.  use
0A2  0A2 1977-79 Rizzato Califfo de Luxe, La Mopette (step thru)
orig.  use
A18  A18 1976-80 Sachs (Hercules) P1, Westlake, Sundancer (sheet frame)
A15  A15 1976-80 Sachs (Hercules) M4, Balboa , Suburban (tube frame) also A18
A15  A15 1980-83 Sachs (Hercules) Seville (sheet frame)
A18  A18 1980-83 Sachs (Hercules) Prima (step-thru)
A18  A18 1980-84 Sachs (Hercules) Prima G3 (top tank)
0A5  0A5 1975-78 Safari (MZV) Ridget, Super, Super Extra (mono tube) also A3
0A5  0A5 1978-80 Safari (MZV) Leader, Cobra (mono tube) also A3
0A3  0A3 1978-91 Safari (MZV) Automix, 300MT (top tanks) also A4, A2
0A3  0A3 1978-91 Safari (MZV) 400MT (has two petcocks, top tank and frame tank)

0A3  0A3 1978-91 Safari (MZV) Variomatic, Commando (top tanks) also A4, A2
0A0  0A6 1977-79 Scorpion (NVT) SC1, SC2, SC2X (mono tube)

A14  A14 1978-79 Sears (Kromag) Free Spirit (all models) also A15
A31  A31 1956-69 Sears (Puch) Allstate Mo-Ped (MS50)
A31  A31 1965-67 Sears (Puch) Allstate Sabre (VZ50) and others, see Puch
0A8  0A2 1978-80 Snark (Italtelai) Standard, Deluxe (step-thru)
0A8  0A4 1978-80 Snark (Italtelai) Satellite (top tank)
0A6  0A6 1970’s    Solex
Tenor 8000 (Laura M54)
0A6  0A6 1974-75 Solex Tenor 8000 (Laura M56) 

A31  A31 1977-83 Sparta Foxi GT, Buddy, Lucky
A32  A32 1974-77 Sparta Lucky (rear tank)
A13  A13 1977-78 Speed Bird (TYM) BP48, BP48-S (tube frame)
A28  A26 1976-78 Sprinter (Tsing Hua) and compatibles 

B16  B16 1980-91 Suzuki FA50 Shuttle
orig.  use
0A7  0A7 1987-94 Tomos Bullet TT, TTLX, Sprint TT
A17  A17 1974-95 Tomos Bullet A3, A35 (all step thru)
A10  A10 1992-95 Tomos Colibri (A35 engine)

A17  A17 1996-06 Tomos Sprint (A35 engine)
A17b A17b ’94-13 Tomos Targa LX, Tomos LX, LX (top tanks)

A20  A20 1996-06 Tomos Targa, Tomos, ST (A35 engine)
A18  A18 2007-13 Tomos Sprint, ST (A55 engine)
A18  A18 2001-13 Tomos Revival, Streetmate, Arrow
A18  A18 2017-18 Tomos Sprint, Sprint Classic, Racing TT
0B1  0B1 1998-02 Tomos TX50, Super Tom, MC36, MC50, MC80
B15  B15 1982-85 Trac (Kia) Clipper (rear tank remote petcock)
B15  B15 1983-85 Trac (Kia) Hawk, Sprint (top tank remote petcock)
A29  A26 1982-85 Trac (Kia) Eagle (step thru sheet frame)
B15  B15 1985-88 Trac (Daelim) Clipper, Escot (step thru rear tank)

A28  A26 1984-88 Trac (Daelim) Image, Sprint (top tank) also A25
B15  B15 1985-89 Trac (Daelim) Olympic, Liberty, Blitz (step thru remote)
A26  A26 1989-90 Trac (Daelim) Metro (step thru rear tank)
orig.  use
A18  A18 1977-79 Vespa (Piaggio) Bravo (metal tank)
0B1  0B1 1975-78 Vespa (Piaggio) Bravo (plastic tank)
A23  A23 1967-90 Vespa (Piaggio) Ciao, Ciao PX
A21  A21 1978-86 Vespa (Piaggio) Grande, Grande MX, Si
orig.  use
0A1  0A1 1957-64 Wards (Motobecane) Riverside Mo-Ped
0A2  0A2 1965-70 Wards (Benelli) Riverside 150D, 250D
A27  A25 1978-79 Wheel King Road Runner, Cuyler (mono tube)
A15  A16 1998-09 Whizzer motorized bikes (with reserve tube removed)
orig.  use
A27  A25 1979-82 Yamaha QT50 Yamahopper
0A3  0A3 1977-79 Yankee Peddler (FMB), also A4 or A2


Gas Valve Parts

C. inline fuel filters, fittings, fuel hoses,
outer seal rings

D. inner seal disks










Gas Valve Info


Fuel Valve (on tank): On or near the bottom of nearly every moped gas tank is a “petcock” or “gas valve” that has a lever or knob for manually shutting the fuel supply off, for when the bike is stored or transported. The reason for the shut off valve is gravity. Moped and most motorcycle gas tanks are higher than the engine and use gravity to move the gasoline out of the tank, instead of a fuel pump. The higher the liquid fuel level is above the carburetor, the higher the fuel pressure will be. If the the tank is too low, or the carb too high, no gas will come out, or it will even flow backwards. Everyone knows that liquids only flow downhill.

Float Valve (inside carb): In addition to the fuel valve, there is an second device, called the float needle or float valve, in the carburetor that shuts off the gas supply automatically. On a new bike with a new carburetor and clean gasoline, the float valve works all the time, so there is no need to turn the gas valve off after each use. On most old mopeds, the float valve leaks sometimes, and needs the operator to manually turn the gas valve off after each use to prevent gasoline from leaking out.

Manual Petcock

Manual Petcock: Most have a handle that rotates to turn the gasoline supply off and on.


Vacuum Petcock

Vacuum Petcock (on tank): On most modern scooters and motorcycles the fuel valve is an automatic type, operated by the vacuum from the engine. When the engine stops, or whenever the suction in the vacuum line stops, the petcock shuts the gas off.


How Reserve Works

On-Off-Reserve: Besides turning the gas on and off, most gas valves also have a third position called “reserve”. Reserve is for when the tank is very low on gas. A little tube 1 or 2 inches long sticks up from the gas valve, inside the tank. When the gas is on “ON”, it exits from the upper end of the tube. When the level of gasoline drops below the tube, no more gas comes out, and the engine dies. This is called “hitting reserve”. The operator then switches the gas valve to “RESERVE”, which make the gas exit from the lower end of the reserve tube, at the very bottom of the gas tank. There is about 5 or 15 miles of gasoline available on reserve, enough to find a gas station. If a gas tank  has rust crumbs, powder, or water droplets at the very bottom, it is better to not use the reserve because it lets dirt get through and will clog easily.


Fuel Valve Types

Bolt-on: Most modern motorcycles use the bolt-on design. The tank has one or two M6-threaded holes spaced about 30-35mm apart, with a 10mm main hole in the middle. A race track shaped rubber ring provides the seal. Angel (made in Taiwan by Tym) is the only pedal moped with a bolt on fuel valve. For some reason, bolt on fuel valves are rare on mopeds, but common on motorcycles.

Screw-on: Almost all mopeds use the screw-on design, where the tank has either a hole with internal threads, (female tank) or a fitting with external threads (male tank). Screw-on fuel valves do not seal at the threads like pipes, but rather have a sealing surface perpendicular to the threads, for a soft paper or plastic washer. They are tightened enough to compress the seal washer.

Female screw-on fuel valves for external thread tanks have the ability to point in any direction, because the valve main body does not screw on, instead only the nut turns. The special nut is a “turnbuckle style” in that it has right hand threads on one end and left hand threads on the other. This allows the valve to fit in tight places. It also means the nut has a top and bottom and won’t go on upside down, unlike a regular nut.

Male screw-on fuel valves for internal thread tanks also have the ability to point in any direction. When the seal washer is soft rubber and thick, and retained by a metal cup, it seals even when the valve is slightly loose and somewhat free to rotate.

Clamp-on: A third type of gas valve is clamp-on, found on Derbi mopeds with a plastic gas tank. It seals against the tank exit pipe semi-flexible soft plastic walls by o-rings squeezing radially inward by a hose clamp.

Spigot Positions

Spigot Direction:  L = left    R = right    D = down    B = back  (as you face the valve). Some models have room for more than one spigot direction. Many mopeds can have any spigot direction, because there is nothing near the petcock that interferes with the fuel hose. Then there may be choices. Other kinds are only available in one spigot direction. Sometimes an original valve that was “spigot down” must be replaced with one that is “spigot left”, and a longer piece of fuel line installed. Sometimes, if the valve is angled, and the spigot direction of the replacement valve is uphill, the new valve can affect fuel flow when the gas tank is really low. If it cannot be rotated and angled more spigot level or downwards, then the lower part of the tank will become unavailable when the liquid level reaches the highest part of the fuel line. That is, it will run out of gas prematurely.

Naming of Gas Valves: Many screw-on gas valves sold online are named by their true size (11,13, or 15mm), rather than their nominal size (12, 14, 16mm). This is a big source of confusion. For a bolt (external or male thread) the nominal (named) size is the true size, so an M6 (metric 6mm) bolt has a diameter of 6mm. But for a nut (internal or female thread), the nominal size is greater than the true size. An M6x1 nut has an internal diameter of 5mm. A 1/4 -20″ nut has an internal diameter of 0.20 inch, not 0.25. The difference between the external and internal diameter is approximately equal to the thread pitch. So a 12×1.00 nut measures 11.00mm inner diameter, while a 12×1.50 nut measures 10.5mm.

Gas valve low cost substitutes:  USA plumbers will recognize that the moped gas valve M10x1 thread is close to 1/8″ (named after the small inner diameter) National Pipe Thread Taper NPT . Because of the taper, a brass 1/8″ NPT (27tpi = 0.94mm) screws on and fits the 10×1 thread OK, because it’s about 9.5mm at first, tapering to 10.2mm. With teflon pipe thread tape, any 10×1 thread gas tank can be adapted with American standard pipe pieces, including shut-off valves. All of those things are sold in home improvement stores nationwide. The good side is those pipe pieces are inexpensive and easy to get. The bad side is they must be cleaned up and re-taped every time they are screwed on and off, and they don’t have any reserve feature. 

Gas valve outer seals: Screw on gas valves, unlike plumbing pipes, seal by a soft or semi soft ring, that is squeezed between the gas tank and the gas valve, as the valve or nut is screwed on tight. Plumbing pipes seal by the threads only, and don’t need a flange and soft ring. The sealing surface on both the tank and the valve must be flat and straight. If a gas tank has a damaged sealing surface, then the outer seal might leak, even when the seal and valve are fine. The remedy for a warped, misaligned or scratched sealing surface, on either the tank or the valve, is careful grinding with a flat spinning disk (with all gasoline evacuated).

Turnbuckle nuts are on female type gas valves. They have both forward and reverse threads. One side has right hand thread and goes to the tank. The other side has left hand thread and goes to the petcock. As the nut is tightened the petcock is drawn toward the gas tank. The seal is a fiber or plastic washer.  


Stepped turnbuckle nuts are adapters that allow a female gas valve to fit a larger gas tank thread than it normally would. Examples are 12×1.0 left stepping up to 16×1.0, 16×1.0 left stepping up to 22×1.0 (shown).