Graphite Exhaust Gasket | Honda CB350 / CB360 / CL450
Chances are the exhaust gasket between your pipe and muffler is either missing or barely holding together. When it fails, exhaust gases escape at the joint before reaching the muffler — you'll hear a popping or ticking sound near the pipe-to-muffler connection and see black carbon deposits around the joint. An exhaust leak at this location can also make carburetor tuning inconsistent.
Why You Need This
This graphite replacement gasket seals the joint between the exhaust pipe and the muffler on your CB350, CL350, CB360, CL360, or CL450. It compresses and conforms to both the pipe end and muffler inlet surfaces when you tighten the joint, creating a tight seal that restores proper back pressure. If you're replacing your mufflers this is a must-have addition, but even if you're just getting your factory exhaust system running right, a fresh set of gaskets makes a real difference.
Fit a fresh one any time that joint comes apart. A graphite gasket takes a set the first time you crush it, so it only seals properly on the install it was squashed for.
Specifications
| Spec | Detail |
|---|
| Replaces OEM Part Numbers | 18392-MK4-000, 18391-317-000, 18391-317-010 |
| Fits Models | CB350 K0–K5 (1968–1973), CL350 K0–K5 (1968–1973), CB360G (1974), CB360T (1975–1976), CL360 K0–K1 (1974–1975), CL450 K0–K6 (1967–1974) |
| Material | Graphite |
| Sold As | Individual (order TWO per bike) |
Note: Sold individually — you need TWO to replace both sides. CL350, CL360, and CL450 owners running the stock scrambler exhaust only need ONE, because one of the exhaust pipes is welded directly to the muffler on CL models.
Note: The CJ360, CB450, and CB500T use a larger diameter exhaust pipe and require a different graphite gasket — see our CJ360 / CB450 / CB500T Exhaust Gasket.
Installation
Difficulty: Beginner
Tools needed: 12mm wrench or socket, flathead screwdriver, wire brush
- Unbolt the 12mm nuts on each exhaust flange at the cylinder head and the mounting nuts on the back of the mufflers. Slide the pipe and muffler assembly off the bike.
- Separate the muffler from the pipe. The old gasket sits inside the muffler inlet — it may be covered in carbon and hard to see at first.
- Pry out the old gasket with a small flathead screwdriver. Clean the mating surfaces on both the pipe end and the muffler inlet with a wire brush until they're free of carbon and debris.
- Slide the new graphite gasket onto the end of the exhaust pipe.
- Reassemble the pipe and muffler, then reinstall the assembly on the bike. Snug the mounting nuts — don't over-tighten. The graphite compresses and conforms to seal the joint. Crush it too far and you'll end up with leaky pipes.
Clean the mating surfaces thoroughly before installing the new gasket. Carbon buildup on the pipe or muffler inlet prevents the graphite from making a proper seal.
Our "5 Small Maintenance Jobs" video covers exhaust gasket replacement as one of the most commonly missed maintenance items on vintage Hondas.
Frequently Asked Questions
Will this fit my CJ360, CB450, or CB500T?
No. The CJ360, CB450, and CB500T have a larger diameter exhaust pipe and use a different graphite gasket (OEM 18392-MK5-000). We sell that one separately — see our CJ360 / CB450 / CB500T Exhaust Gasket.
Do I need one or two gaskets?
Most bikes need TWO — one for each side. The exception is the CL scrambler models (CL350, CL360, CL450) with the stock exhaust system, where one pipe is welded directly to the muffler. In that case you only need ONE.
What's the difference between the graphite gasket and the copper exhaust gasket?
They go in different locations. This graphite gasket seals the joint between the exhaust pipe and the muffler. The copper gasket seals the joint between the cylinder head exhaust port and the exhaust pipe. Most bikes need both — copper at the head, graphite at the muffler. We sell copper exhaust gaskets for the CB350 / CB360 and the CB450 / CB500T.
How do I know if my exhaust gasket is bad?
Look for black carbon deposits around the pipe-to-muffler joint — that's exhaust gas escaping past the gasket. You may also hear a ticking or popping sound near the muffler, especially at idle.
Can I reuse these gaskets?
No. Graphite crush gaskets are a one-time-use part. Once one is fully crushed it takes a set, and clamping the same gasket down again will not give you a reliable seal. The copper crush gaskets at the cylinder head are the ones that stretch further, usually three or four torquings before they need replacing.
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Last updated: March 2026
