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1978 Honda CB400A Gaskets & Valve Seals

A leak at the valve cover and oil passing a valve guide call for different parts on the 1978 Honda CB400A. Compare the repair location first, then choose a separate cover gasket or the individually supplied CB400A valve-stem seal.

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Honda CB400 Athena overhaul gasket set

1978-81 Honda CB400 Athena Overhaul Gasket Set

$119.95 USD
18-0103
Rebuild your CB400 engine with this Athena Overhaul Engine Gasket Set. Athena of Italy is an original-equipment supplier to Yamaha, Honda, Kawasaki, Suzuki, and...
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Honda CB450 CB400 valve cover gasket 12328-413-830

1978-86 Honda CB450 / CB400 Valve Cover Gasket ~ Replaces 12328-413-830

$31.95 USD
12-1014
Replace your CB400 or CB450 valve cover gasket with this Athena Brand Valve Cover Gasket, replacing OEM #12328-413-830. Fits the full CB400A/TI/TII/T range plus...
Honda CB400A valve stem seal 12209-413-003

1978 Honda CB400A Valve Stem Seal

$2.31 USD
01-0127
Valve Stem Seal ~ Replaces Honda OEM 12209-413-003 for the Honda CB models listed below. Use this part for repair, restoration, or replacement work...
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1978 Honda CB400A · Gaskets & Valve Seals Buying guide

Choose the seal at the actual repair point

The separate Athena cover gasket and CB400A-specific valve-stem seal provide clear repair choices. Keep top-end sealing work separate from the Hondamatic’s crankcase and transmission-cover requirements when planning a larger rebuild.

Parts to consider

1978-86 Honda CB450 / CB400 Valve Cover Gasket ~ Replaces 12328-413-830 Athena valve-cover gasketSeparate valve-cover gasket for the CB400A. Replaces reference 12328-413-830.View part 1978 Honda CB400A Valve Stem Seal CB400A valve-stem sealAftermarket replacement for reference 12209-413-003. Sold individually.View part

A cover gasket is a focused purchase

The Athena gasket replaces reference 12328-413-830 and is specifically listed for the 1978 CB400A. Compare the cover outline and the existing gasket before ordering, particularly if the engine or cover has been replaced during the motorcycle’s life.

Build the order from the repair plan

The CB400A valve-stem seal is sold each under reference 12209-413-003. Count the seal positions included in your planned work. For a broader overhaul, obtain a component list that covers the Hondamatic joints you will actually open before choosing an assortment.

Gaskets & Valve Seals questions

Is the valve-stem seal supplied as an engine set?

No. The CB400A-specific replacement is sold individually. Order for the positions being serviced; do not use a quantity printed for a different Honda engine.

Which gasket is intended for the valve cover?

Choose the separate Athena valve-cover gasket with reference 12328-413-830. It is listed for the 1978 CB400A and lets you order for that joint without assuming overhaul-set contents.

What should I confirm before buying an overhaul gasket set?

Check an itemized contents list against every joint being opened, including Hondamatic-specific covers. A CB400 family application does not describe which individual case gaskets, seals or O-rings are supplied.

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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