Mufflers on your Honda CB350 are often rusted through, missing, or replaced with an ill-fitting aftermarket exhaust. While our replacement mufflers are not factory clones, they retain a period-correct look and can be installed cleanly with the correct hardware, bracket setup, and gaskets.

Why these mufflers work so well on the Honda CB350

Original Honda mufflers are incredibly difficult to find in usable condition, with most available sets either being very expensive or filled with rust holes. Even when the exterior looks good, the internal baffling has often rusted apart. Without intact baffling, the mufflers cannot properly regulate exhaust flow and back pressure, which can create performance inconsistencies between the left and right cylinders.

These mufflers are sized appropriately, sound great, and look correct on the CB350 family of motorcycles. The baffles are also removable, which makes future cleaning or repacking possible.

Parts Needed

• Pair of Common Motor mufflers (#5002)
• Muffler mounting hardware - Comes with the Common Motor mufflers
• Stainless T-bolt clamps - Comes with the Common Motor mufflers
• Graphite crush gaskets for header pipe to muffler connection
• Copper crush gaskets for header pipe to cylinder head
• Anti-seize compound
• Red thread locker
• 3/4 inch automotive heater hose
• Clear nail polish, paint, or another rust-preventive coating for modified bracket edges

Tools Needed

• Metric hand tools
• Allen wrench for baffle screws
• Flathead screwdriver
• File
• Hacksaw
• Step drill bit
• Adjustable wrench

What hardware is included with the mufflers

Each muffler set includes the mufflers themselves, curated mounting hardware, chrome one-bolt clamps, stepped metal adapter collars, and stainless steel T-bolt clamps. 

Muffler hardware overview

Optional Recommended Parts

The graphite crush gasket is the preferred seal between the header pipe and muffler. This is closer to the original Honda sealing approach and gives a cleaner result than the stepped metal adapter collars.

Note: The graphite crush gaskets are one-time-use parts once fully compressed.

The copper crush gaskets at the cylinder head are also commonly overlooked. If the header pipes are being removed or disturbed during installation, replace these gaskets so the header pipe seals correctly at the cylinder head.

Inspecting and servicing the removable baffles

These mufflers use a removable mechanical baffle retained by three Allen screws.

If you plan to inspect or repack the baffles, do that while the mufflers are new. The screws are easier to remove before heat cycles, rust, and carbon buildup make the assembly harder to disassemble.

Baffle service notes

• Remove the three Allen screws carefully.
• Pull the baffle assembly straight out of the muffler.
• Apply a light amount of anti-seize to the baffle end and fastener threads before reassembly.
• Do not overtighten the baffle screws.

If additional muffler packing is used, keep the packed diameter within the inner size of the muffler body so the baffle can slide back into place.

Mounting the Mufflers on the CB350

Use the factory Honda muffler mounting brackets if you still have them. If the factory brackets are missing, modify the included universal brackets.

Reusing the factory CB350 muffler brackets

The factory brackets are the preferred option because they provide two easy attachment points from the muffler to the bracket. This gives the muffler a more secure mount and a cleaner finished look.

The recommended hardware arrangement uses special square nuts inside the muffler bracket channel. These square nuts provide more surface area than a standard bolt head and reduce the risk of pulling through the muffler mounting channel.

Factory bracket hardware arrangement

Important installation note

Mock up the bracket loosely first. Exhaust systems on vintage motorcycles often require slight movement because header pipes, frame tabs, and brackets may not be perfectly aligned after years of use.

Only apply red threadlocker after the entire system is aligned and you are committed to the final position.

Modifying the included universal brackets

If the factory brackets are missing, the included universal chrome strap brackets can be modified into a solid dual-mount setup using a few simple hand tools.

Universal bracket modification steps

1. Identify the two universal bracket straps.
2. Mark the cut location approximately between the center holes as shown in the video process.
3. Cut the bracket with a hacksaw.
4. Deburr the cut edges and round the corners with a file.
5. Enlarge the selected mounting holes one size larger with a step drill bit so the factory frame bolt fits as shown in the video.
6. Deburr the drilled holes.
7. Seal all exposed raw metal edges and drilled surfaces with clear nail polish, paint, or another protective coating.

Modified universal bracket orientation

• Install the longer bracket section toward the rear.
• Overlap the longer and shorter sections on the inside face of the muffler bracket.
• Keep the rough cut edges facing inward where they are less visible.
• Use the enlarged hole at the frame mounting point.

Why the square nuts matter here

The modified universal bracket still benefits from the same square nut arrangement used with the factory bracket. The square nut gives the bracket channel more support and helps prevent the bracket from tearing out under load.

Header pipes and exhaust gaskets

Before fitting the mufflers, inspect the header pipes and replace any worn sealing parts.

Header pipe notes for CB350 models

Most Honda CB350 motorcycles use separate header pipes and mufflers. Some earlier motorcycles may have a header pipe and muffler welded together as a single assembly. On those motorcycles, the damaged muffler must be cut away to expose the remaining usable header pipe section.

Some earlier motorcycles may also use different flange details and smaller studs at the cylinder head. Inspect your hardware before beginning final assembly to ensure you are assembling using the same hardware and exhaust collars that were on the bike when you disassembled it.

Preparing the cylinder head connection

1. Inspect the cylinder head exhaust port for the old copper crush gasket.
2. Use a small flathead screwdriver or pick to remove the old gasket if it is still in place.
3. Install a fresh copper crush gasket.
4. Position the seam of the gasket inward.

Preparing the header pipe

1. Clean carbon and residue from the end of the header pipe.
2. Apply a light amount of anti-seize where appropriate on the cylinder head exhaust studs.
3. Slide the graphite crush gasket onto the end of the header pipe.
4. Confirm the gasket sits flush and square.
5. If the muffler end is slightly too small, gently open the slots on the end with an adjustable wrench so the muffler can slide on smoothly.

Caution: Do not over-compress the copper crush gasket at the cylinder head. Tighten only enough to stop movement and create a seal.

How to install the mufflers with factory brackets

This is the preferred installation method when the original CB350 muffler brackets are available.

Installation steps

1. Install the factory brackets onto the mufflers using the square nuts, bolts, split lock washers, and flat washers.
2. Leave the bracket hardware slightly loose.
3. Loosely install the header pipes at the cylinder head with the exhaust collars and nuts.
4. Place the stainless T-bolt clamp over the muffler inlet.
5. Apply a small amount of anti-seize to the clamp threads and the clamp seat.
6. Slide the graphite gasket onto the cleaned header pipe.
7. Fit the muffler onto the header pipe.
8. Align the end of the muffler with the stop ring on the header pipe.

9. 

   Do not slide the muffler past or over the stop ring as it will prevent the muffler from clamping the graphite gasket fully.

10. Install the frame mounting bolt through the bracket and leave it slightly loose.
11. Adjust the muffler position, bracket position, and clamp position until the system sits naturally.
12. Snug the T-bolt clamp.
13. Snug the header fasteners at the cylinder head.
14. Tighten the frame mounting hardware.
15. Tighten the bracket-to-muffler hardware.
16. Once satisfied with fitment, remove one bracket bolt at a time, apply red threadlocker if desired, and reinstall.

T-bolt clamp positioning

For this CB350 setup, the T-bolt clamp should be clocked so the bolt faces upward and the clamp sits cleanly between the frame rails.

How to install the mufflers with modified universal brackets

Use this method when using the included universal brackets.

Installation steps

1. Install the modified bracket sections onto the muffler with the square nuts and hardware.
2. Keep all bracket hardware loose enough to move during alignment.
3. Loosely install the header pipe at the cylinder head.
4. Place the T-bolt clamp on the muffler.
5. Install the graphite crush gasket on the header pipe.
6. Slide the muffler onto the header pipe.
7. Align the muffler inlet with the stop ring on the header pipe. 
8. Do not slide the muffler past or over the stop ring as it will prevent the muffler from clamping the graphite gasket fully

9. 

   Install the frame mounting bolt and nut loosely.

10. Adjust the bracket overlap and rotation until the muffler sits square on the motorcycle.
11. Snug the T-bolt clamp.
12. Snug the header nuts.
13. Snug the frame bolt.
14. Make any needed adjustments before final tightening.
15. Apply red threadlocker to the bracket bolts only after the final position is confirmed.

Foot peg clearance note

On some motorcycles, this mounting area may also be used by the foot peg assembly. If the foot peg interferes with the modified bracket, the peg mount may need to be trimmed, shortened, or bent to clear the muffler bracket.

Final tightening, alignment, and service notes

Once the muffler, header pipe, bracket, and clamp are all in the correct position, tighten the entire system evenly.

This is the stage where final threadlocker can be applied to the bracket bolts if desired.

Final checks

• Muffler is seated correctly before the stop ring
• Clamp is centered and properly rotated to a position that is not in the way of the shifter or frame
• Header pipe is sealed at the cylinder head
• Muffler bracket is not under tension
• Muffler does not contact the frame
• All hardware is tightened evenly

Important future service note

If the exhaust assembly needs to come off later, remove the muffler and header pipe assembly from the motorcycle as one piece when possible. Remove the large frame bolts that connects the muffler hanging bracket and the header exhaust flange nuts to pull the exhaust system off as a single piece.

Do not separate the muffler from the header pipe unless you are prepared to replace the graphite crush gasket.

How to protect the mufflers from stand contact

The factory mufflers used built-in stand bumpers. These replacement mufflers do not. Without protection, the side stand and center stand can strike the muffler and leave dents or marks over time.

A simple solution is to slide short sections of 3/4 inch automotive heater hose over the contact points on the stands.

Heater hose bumper lengths shown in the video

Use tire lube, soapy water, or a similar lubricant to slide the hose into place.

Troubleshooting

The muffler will not slide onto the header pipe

Clean the pipe end thoroughly and inspect for deformation. If the muffler end is slightly compressed, gently open it just enough for the muffler to slide on over the graphite gasket.

The muffler joint leaks

Verify that the graphite crush gasket is installed and that the muffler has not been pushed over the stop ring. Recheck clamp position and clamp tension.

The muffler does not line up with the frame mount

Loosen the entire system again. On vintage exhaust systems, the header pipe, muffler, and brackets often need to float into position before final tightening.

FAQ

Can I reuse the factory muffler mounting brackets on a Honda CB350?

Yes. The factory brackets are the preferred option because they provide a cleaner and more secure two-point mount.

Should I use the metal adapter collars that come with the mufflers?

We do not recommend them for this CB350 installation when graphite crush gaskets are available.

Do I need to replace the copper crush gaskets at the cylinder head?

Replace them if they are flattened, damaged, missing.

Can I remove the baffles from these mufflers?

Yes. The baffles are removable and can be inspected, cleaned, or repacked.

Should I use threadlocker on the muffler hardware?

Yes, on the bracket bolts if desired, but only after the full exhaust system is mocked up and aligned.

Can I separate the muffler from the header pipe later for service?

You can, but it is not recommended if you want to preserve the graphite crush gasket. Remove the assembly together when possible.