Honda Bond 4 Gasket Sealer for Vintage Honda Motorcycles
Honda Bond 4 is the correct semi-drying liquid gasket sealer specified by Honda for aluminum engine cases on vintage motorcycles. This latex acetone-based sealer is chemically different from off-the-shelf RTV silicone — it bonds to aluminum, stays pliable, and is meant specifically for aluminum case components coming together.
Important (January 2025): Due to supply chain issues, Honda Bond 4 may be substituted with an equivalent gasket sealer (Three Bond Gasket Sealer or Permatex MotoSeal Gasket Maker) based on availability. All of these products are the proper latex acetone-based sealer needed for aluminum engine cases on your vintage Honda — not off-the-shelf RTV silicone. If you have questions about any of these sealers, please contact us before placing your order.
Why Honda Bond 4 — Not RTV Silicone
RTV silicone is sold at every auto parts store, but it is not the correct sealer for vintage Honda motorcycle engines. As demonstrated in our CB350 engine rebuild series, Honda Bond is "a latex acetone-based sealer — it's not RTV silicone... it's meant specifically for aluminum case components coming together." RTV silicone is a different product with different chemistry. We regularly see engines assembled with RTV silicone that leak because of it.
Where to Use Honda Bond 4
Honda Bond 4 is used anywhere aluminum parts mate face-to-face without a paper gasket in between:
- Crankcases: Applied to both mating surfaces of upper and lower crankcase halves on CB350, CB360, CB450, CB500T, CB550, and CB750 engines.
- Valve covers: On models where the valve cover seals directly to the cylinder head without a paper gasket (late CB125SA, CB360), Honda Bond 4 is the sealing agent.
- Cylinder base gaskets: A small amount around the oil passages of the upper crankcase and bottom of the cylinder helps seal the base gasket at those critical oil passage points.
- Oil seals: A light coat on the outer perimeter of oil seals (shift shaft, output shaft) before pressing them into the case helps ensure a leak-free fit.
- Fork drain bolts: A small amount on the threads of fork lower leg drain bolts acts as a thread sealant during fork rebuilds.
How to Apply Honda Bond 4
- Clean surfaces thoroughly. Use carb cleaner or acetone to remove all oil, grease, and old sealer from both mating surfaces. Surfaces must be completely clean and dry before application.
- Apply a thin, even coat to both sealing surfaces. Spread it out with a gloved finger or Q-tip — think of applying the most even coat of butter on toast. Do not squeeze the sealer on like toothpaste.
- Work promptly. Once you start applying Honda Bond, you need to commit and keep moving. Have all your parts ready before you begin.
- Assemble and torque. Bring the parts together, install bolts hand-tight, then torque to spec. A small bead of sealer squeezing out at the seam is normal — it means you have full coverage.
Tip: For small or hard-to-reach areas like seal bores and oil passages around cylinder base gaskets, use a Q-tip to apply the sealer precisely. For larger surfaces like crankcase halves, a gloved finger works best for spreading a thin, even coat.
Specifications
| Type | Semi-drying liquid gasket sealer |
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| Base | Latex acetone |
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| Size | 80ml tube |
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| Coverage | One tube covers multiple engine rebuilds |
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| Also Known As | Three Bond, Yama-Bond, HondaBond, liquid gasket |
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| Equivalent Products | Three Bond Gasket Sealer, Permatex MotoSeal Gasket Maker |
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| Not a Substitute For | RTV silicone (different chemistry — not correct for aluminum engine cases) |
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Our Honda CB350 / CL350 engine rebuild video demonstrates the correct application of Honda Bond 4 on crankcase surfaces and oil seals — including surface preparation, application technique, and torque sequence.
Frequently Asked Questions
Can I use RTV silicone instead of Honda Bond 4?
No. RTV silicone is a different product with different chemistry. Honda Bond 4 is a latex acetone-based sealer designed specifically for aluminum engine cases. We regularly see engines assembled with RTV silicone that leak. Use only Honda Bond 4, Three Bond, or Permatex MotoSeal.
How much Honda Bond 4 do I need for an engine rebuild?
One 80ml tube is enough for multiple complete engine rebuilds. You only need a very thin coat on each mating surface — applying too much is a common mistake that can cause sealer to squeeze into oil passages.
Where on the engine do I NOT use Honda Bond 4?
Do not use Honda Bond 4 where a paper gasket or rubber O-ring provides the seal. Honda Bond is for aluminum-to-aluminum surfaces without a gasket, and as supplemental sealing around oil passages on base gaskets.
Is this the same product as Three Bond or Yama-Bond?
Yes. Honda Bond 4, Three Bond, and Yama-Bond are all the same type of latex acetone-based liquid gasket sealer. The names come from different manufacturers and OEM branding, but they are functionally equivalent products.
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Last updated: March 2026
