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1978 Honda CB400A Fuel Caps & Petcocks

The 1978 Honda CB400A tank-parts choices cover the filler cap, fuel valve and front mounting rubbers. Start by checking whether the tank is original. A replacement tank can change the cap opening, petcock connection or support arrangement even on an otherwise standard motorcycle.

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Currently viewing Gas Tanks, Caps, Petcocks & Parts

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Honda CB750 CB550 CB450 CB400 CB350 gas cap rubber seal 17631-329-003

Honda CB Gas Cap Rubber Seal ~ Replaces 17631-329-003

$7.95 USD
20-0097
Replace the broad-fitment gas cap rubber seal on many classic Hondas with this Gas Cap Rubber Seal, replacing OEM #17631-329-003. Exceptionally wide fitment covering...
Honda CB750 CB550 CB400 filler cap 17620-399-010

Honda CB750 / CB550 / CB400 Filler Cap ~ Replaces 17620-399-010

$69.95 USD
73-0079
Replace your gas tank cap with this OEM Style Gas / Fuel Tank Cap with rubber gasket already installed, replacing OEM #17620-399-010.Note: does not...
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Honda CB400 fuel petcock 16951-385-703

1978-81 Honda CB400 Fuel Petcock ~ Replaces 16951-385-703

$15.82 USD
29-0543
Keep fuel flowing reliably to your carburetors with this Fuel Petcock, designed as a direct replacement for several original Honda fuel valve assemblies. This...
Honda CB front fuel tank rubber cushion 17611-KE8-000

Front Fuel Tank Rubber Cushion ~ Replaces Honda OEM 17611-KE8-000

$5.50 USD
27-5520
This aftermarket front fuel tank rubber cushion replaces Honda OEM 17611-KE8-000 on the listed Honda CB-series applications. It mounts to the frame and supports...
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1978 Honda CB400A · Fuel Caps, Petcocks & Mounts Buying guide

Match each replacement to the tank on the bike

A cap with its gasket, a threaded fuel valve and individually supplied front cushions address different needs. Compare each connection directly before ordering, particularly when restoring a motorcycle with a changed fuel tank.

Parts to consider

Honda CB750 / CB550 / CB400 Filler Cap ~ Replaces 17620-399-010 Fuel-tank filler capOEM-style cap with rubber gasket installed, reference 17620-399-010. No retaining chain is included.View part 1978-81 Honda CB400 Fuel Petcock ~ Replaces 16951-385-703 Fuel petcockReplacement fuel valve with M16 × 1.5 tank thread, listed for the 1978 CB400A.View part Front Fuel Tank Rubber Cushion ~ Replaces Honda OEM 17611-KE8-000 Aftermarket front tank cushionFront fuel-tank mounting rubber replacing reference 17611-KE8-000. Sold individually; order two when replacing both front cushions.View part

Related parts: Separate fuel-cap rubber seal

Choose the cap package intentionally

The OEM-style filler cap comes with a rubber gasket already installed and does not include a retaining chain. If the existing cap is sound, the related replacement rubber seal provides a more focused purchase. Compare the cap and seal reference before choosing between them.

Check the valve and mount independently

The fuel valve uses an M16 × 1.5 tank thread. The front cushion is an aftermarket rubber support sold each. Verify the tank’s connection, outlet clearance and mounting shape separately; a match at one point does not establish compatibility at the others.

Fuel Caps, Petcocks & Mounts questions

Does the replacement cap include its rubber gasket?

Yes. The OEM-style cap has a rubber gasket already installed. It does not include a retaining chain, so account for that when comparing it with the cap currently on the tank.

Can I reuse this petcock on a non-original tank?

Check the M16 × 1.5 connection, fuel-hose outlet position and available clearance first. Its CB400A application describes the original fitment, not every tank that may have been fitted later.

Is the front tank cushion a pair or a single?

The featured aftermarket cushion is sold individually. Order two if replacing both front cushions, and compare the original rubber shape and mounting points before buying for a modified tank.

Not sure which part you need?

Send your model and year, plus photos of your existing part and any changes to the original setup.

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