Exhaust Collars | Honda CB350 / CL350
The split collars are what clamp your header pipes to the cylinder head, and they commonly go missing. If yours are gone, or you have never seen them because the last owner left them out, these are the replacements.
Why You Need This
Each collar is a two-piece split ring that sits between the exhaust header and the nuts holding it to the head. Honda calls it a double split exhaust pipe collar. The collar and the exhaust gasket are what seal that joint — leave the collar out and the pipe will not seat or seal.
These are genuine OEM Honda parts. They may not look exactly like the originals, but they fit the bikes listed below.
Specifications
| Spec | Detail |
|---|
| Replaces OEM Part | 18233-318-000 |
| Honda Part Name | Double split exhaust pipe collar |
| Fits Models | CB350 K2–K5, CL350 K2–K5 (1970–1973). K0 and mid-production K1 need the longer collar — see below. SL350 K0 — see notes |
| Sold As | Each unit is one half-collar and the cart takes multiples of two. Two halves make one cylinder’s collar — order 2 for one cylinder, 4 to do both. |
How many to order. Two halves make one complete collar, which covers one cylinder. So one cylinder takes 2 and a full bike takes 4. It is a question we get asked a lot, and ordering 2 when you meant to do both sides is easy to do.
Model-Specific Notes
- The asterisked years in the chart: K0 and mid-production K1 bikes use a different, longer collar. Those header pipes have a much thinner flange where they meet the copper gasket, so they need a collar roughly an inch longer than ours. Honda’s originals for those bikes are obsolete — used or new old stock only. Fitting K2-and-up header pipes, which have the thicker flange, lets our collars work properly.
- How to tell which one you have. Look at the studs in the cylinder head rather than trying to pin down your K designation. The early bikes use M6 studs; later bikes use M8. Some early bikes also have the header pipe and muffler welded together as a single assembly. This is also the check to run if you have an asterisked SL350 K0. Match what came off the bike.
- CB360 / CL360: a different collar. Order our Exhaust Collars | Honda CB360 / CL360 instead.
- CB450, CB500T and XL350: those take Honda 18233-283-010, which we do not stock and which is no longer available new.
Installation
Difficulty: Beginner
Tools needed: 12 mm wrench or socket, anti-seize
- Back the exhaust flange nuts off with a 12 mm wrench and pull the header pipe clear.
- Put anti-seize on the exhaust stud threads while the pipe is off. They get hot, and they are miserable to deal with once they seize.
- Fit the collar halves around the header with the beveled side facing out toward the flange and the flat side facing in toward the engine. The flat side is what pushes the pipe into the gasket.
- Install the exhaust pipe gasket at the head, then fit the pipe joint with the collar and start the nuts. Leave everything loose.
- Install the muffler, then go back and tighten the exhaust flange nuts. Doing it in that order matters — tighten the flange nuts first and the muffler becomes difficult to fit.
Snug, not tight. There is no factory torque figure for this joint. Tighten until the pipe firms up and stop. Keep going and you crush the copper gasket further than it needs, which costs you the reuses you would otherwise get out of it.
Frequently Asked Questions
How many do I need to order?
Two per cylinder, four for the whole bike. Each unit is one half of a collar, and it takes two halves to make one complete collar around a header pipe.
Which way do the collars face?
Beveled side out toward the exhaust flange, flat side in toward the engine. If a joint will not pull up tight, check the orientation first.
Will these fit my 1968 CB350 or CL350?
Probably not as it sits. K0 and mid-production K1 bikes came with thinner header flanges and a longer collar that Honda no longer makes. Check the cylinder head studs — M6 means you have the early setup and need the long collar, M8 means ours will fit. Swapping to K2-and-up headers is the usual way people solve it.
Should I replace the exhaust gaskets while I am in there?
Yes. The copper crush gaskets sit in the exhaust port right where you are working. A copper gasket is generally good for about three or four torquings before it needs replacing, and they are usually buried under carbon by the time you get to them.
Do these fit a CB450 or CB500T?
No. Those use a different Honda collar that we do not stock and that is no longer available new.
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Last updated: August 2026
