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1978 Honda CB400TII Hawk II Tank Caps & Petcocks

The tank fitted to your Hawk II determines the right cap and petcock. Compare the filler opening, existing cap and threaded fuel-valve connection before ordering, especially on a restored motorcycle whose tank may have been changed during an earlier repair or custom build.

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Most orders ship same or next business day Fitment guarantee Listed for your exact model and year? We’ll make it right if it doesn’t fit as described. Mechanic-backed support Ask our team for help choosing the right Honda CB part.
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 CB400TII Hawk II · Tank Caps & Petcocks Buying guide

Check the tank fittings before choosing its service parts

The petcock uses an M16 × 1.5 connection. For the filler, choose a complete stock-style cap with installed gasket or a separate rubber seal for a serviceable matching cap.

Parts to consider

1978-81 Honda CB400 Fuel Petcock ~ Replaces 16951-385-703 M16 × 1.5 fuel petcockReplacement fuel valve with a 16 × 1.5 tank connection, listed for the Hawk II. Compare the tank fitting and outlet clearance.View part Honda CB750 / CB550 / CB400 Filler Cap ~ Replaces 17620-399-010 Stock-style fuel capReplacement filler cap with its rubber gasket already installed; supplied without an attached retaining chain.View part Honda CB Gas Cap Rubber Seal ~ Replaces 17631-329-003 Fuel-cap rubber sealSeparate cap seal replacing reference 17631-329-003 for the listed original-style Hawk II cap arrangement.View part

Trace a tank-area leak accurately

Locate whether fuel escapes at the filler, valve mounting or another connection before ordering. Check the condition of the tank and its fittings too. A new cap seal or petcock should address an identified fault, rather than mask damaged surrounding components.

Choose the cap repair at the right level

The complete stock-style cap arrives with its rubber gasket fitted and has no attached retaining chain. A separate seal suits a sound matching cap. Compare the cap’s engagement with the tank and avoid buying duplicate seals for a straightforward complete-cap replacement.

Common questions

Will the petcock work with an aftermarket tank?

Check the tank connection for M16 × 1.5 threads, then compare the valve outlet and available clearance. A changed tank must be assessed by its actual fittings rather than the original motorcycle’s model.

Does the complete cap include a gasket?

Yes. The rubber gasket is already installed in the complete stock-style cap. It is supplied without an attached retaining chain, so account for that detail when planning an original-style restoration.

When should I choose the separate cap seal?

Choose it when the existing cap is the matching type and remains mechanically sound. If the cap’s engagement or other structure is damaged, inspect the complete-cap option instead of expecting a new seal to solve that problem.

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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