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  • 1969-71 Honda CB750K Exhaust Diffuser Baffle ~ Genuine Honda 18311-300-320 ~ Replaces 18311-300-320
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Honda CB750K exhaust diffuser baffle 18311-300-320
Honda CB750K exhaust diffuser baffle 18311-300-320 — OEM fiche location reference
Honda CB750K exhaust diffuser baffle 18311-300-320
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Honda CB750K exhaust diffuser baffle 18311-300-320

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Load image into Gallery viewer, Honda CB750K exhaust diffuser baffle 18311-300-320 — OEM fiche location reference
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1969-71 Honda CB750K Exhaust Diffuser Baffle ~ Genuine Honda 18311-300-320 ~ Replaces 18311-300-320

99-5235
$89.95 USD

Sold individually

In stock Usually ships the same or next business day
Check model fitment View fitment
Questions about this part? Contact us 4.8/5 1,330 store reviews
Secure checkoutProtected payment
60-day returnsEligible unused parts Free ground shippingUSA & Canada over $50
Browse all parts
1969-71 Honda CB750K Exhaust Diffuser Baffle ~ Genuine Honda 18311-300-320 ~ Replaces 18311-300-320
$89.95 USD
Description

This genuine Honda exhaust diffuser baffle fits inside the original CB750K HM300 muffler to help control exhaust sound and backpressure. It is a smart replacement when the original exhaust diffuser, muffler baffle, exhaust baffle, or diffuser pipe is missing, damaged, or heavily corroded.

Use this OEM Honda exhaust diffuser baffle for CB750K restoration work, original exhaust service, and stock muffler repairs where the correct internal baffle matters.

Key Features

  • Genuine Honda OEM part.
  • Honda OEM number: 18311-300-320.
  • Exhaust diffuser baffle / muffler baffle / exhaust diffuser pipe.
  • Fits original HM300-style CB750K0-K1 exhaust pipes.
  • Sold individually.
  • Most applications use 4 per motorcycle.
  • Compare your original muffler style and OEM number before ordering, especially if the motorcycle has aftermarket or replacement exhaust pipes.

Fitment / Compatibility

  • Honda CB750K (1969-1971)
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Check the listed model and year, then read any fitment notes in the description.

Make Model Year
Honda CB750K Standard 1969
Honda CB750K 1970
Honda CB750K 1971

Free ground shipping over $50

To the USA & Canada. In-stock orders usually ship from our own warehouse the same or next business day.

Estimated ground delivery after your order ships
DestinationDelivery time
USA4–7 business days
Canada2–6 business days

Ground shipping includes tracking, emailed when your order ships. Need it sooner? Express options are available at checkout.

See full shipping details

60-day returns on eligible parts

No restocking fees. Eligible parts must be unused, uninstalled, unaltered and complete. The 60-day window starts when your order is delivered.

Electrical parts are excluded from standard returns. Check return eligibility.

Start your return below. Wait for our instructions before mailing a part back.

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Other shipping options

Canada Post Economy: Available at checkout for select small items. Allow 1–3 weeks for delivery. No tracking or insurance is included.

Outside the USA & Canada: Delivery times vary by destination and shipping method. Buyers are responsible for applicable duties, taxes and import fees. We cannot mark orders as gifts.

Frequently Asked Questions

How many genuine Honda HM300 exhaust baffles are included and required?

One diffuser baffle, Honda OEM 18311-300-320, is included. The original four-pipe HM300 exhaust on the compatible 1969-1971 CB750K0/K1 uses one baffle per muffler, so four are required for all four outlets.

Will OEM 18311-300-320 fit an aftermarket CB750 exhaust?

Not automatically. It is intended for the original HM300-style muffler outlet. Measure the outlet and compare the retaining arrangement before ordering for a reproduction or modified exhaust.

What should be inspected when replacing an exhaust baffle?

Check the muffler outlet, retaining screw or hardware and internal support for corrosion or damage. The baffle must be secured so it cannot loosen or obstruct exhaust flow.

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