How do you re-pack an Arrow exhaust muffler correctly?

You twist the throttle, expecting that deep, sporty Arrow roar—but instead, you’re greeted by a hollow, tinny rasp that sounds more broken lawnmower than precision-engineered Italian exhaust.

Table of Contents

Here’s the truth about performance mufflers: they don’t stay perfect forever. That distinctive Arrow exhaust note comes from sound-absorbing packing material inside the can. Over time, heat and exhaust pulses cook that packing into dust, burn it away, or blow it out the back . The result? Your bike gets louder in all the wrong ways—raspy, unpleasant, and often down on power because the exhaust system no longer functions as designed . The good news? Repacking your Arrow muffler is a satisfying weekend job that costs a fraction of a new exhaust and restores that new-pipe magic.

TL;DR;

Repacking your Arrow exhaust involves removing the end cap (usually riveted), extracting the old burnt packing, wrapping the perforated core with fresh sound-absorbing material, and reassembling with new rivets . Most Arrow systems are “absorptive” mufflers that rely on fiberglass or steel wool packing to dampen sound waves . Over time, this packing degrades—after as little as 50 hours on hard-used bikes or 6,000 miles on street bikes . Signs you need a repack include raspy sound, visible smoke from the can, discoloured carbon fibre, or perceived power loss . Packing materials vary—FMF, Silent Sport, and Athena all offer quality options—but the key is correct density and installation technique .

Key Takeaways

When to Repack: If your exhaust sounds raspy, tinny, or noticeably louder in a bad way—time to act
Signs of Burnout: Discoloured carbon fibre, melted stickers, or smoke from the can indicate packing failure
Tools Needed: Drill (for rivets), rivet gun, safety gloves, packing material, possibly stainless steel mesh
Material Options: FMF 4-stroke packing, Silent Sport, Athena glass wool—each with different lifespan claims
The Mesh Trick: Wrapping the core in stainless steel window screen before packing extends material life significantly
Packing Density: Crucial balance—too tight kills sound and flow, too loose doesn’t absorb enough
Rivet Reality: You’ll need a strong rivet gun—cheap ones struggle with stainless rivets
Performance Impact: Proper repacking restores power, throttle response, and that sweet Arrow tone

Why Your Arrow Exhaust Needs Repacking

Have you ever wondered what’s actually inside that sleek carbon or stainless can? Arrow exhausts are typically “absorptive” mufflers—they use a straight-through perforated core surrounded by sound-absorbing material . Exhaust gases flow through the core, and sound waves pass through the perforations into the packing, where they’re absorbed and converted into tiny amounts of heat.

Here’s the problem: that packing lives in a brutal environment. We’re talking extreme heat, high-pressure pulses, and constant vibration. One forum member described opening their Arrow after 60 hours: “80% of wool had vanished, burnt, carbonized” . Another noted their stock packing was “completely gone at 285 hrs” .

What Happens When Packing Fails

When packing degrades, several things happen:

Sound goes nasty: That deep, controlled Arrow note turns into a harsh, raspy racket
Heat builds up: Packing insulates the outer sleeve—without it, carbon fibre can discolour, crack, or even develop holes
Power drops: The exhaust no longer functions as engineered; one racer reported “big loss of power” before repacking
Backpressure changes: Modern four-strokes are sensitive to exhaust tuning—blown packing alters the whole system

One racer described the progression: “Two or so race weekends I noticed discoloration and the heat resistant sticker kinda melting. Third weekend even more trouble… Following weekend the darn carbon fiber has a big hole in it and big loss of power” .

When Should You Repack?

General Guidelines

Different sources suggest different intervals:

Race bikes: Every 50-60 hours maximum
Street bikes: Every 6,000-10,000 miles
Two Brothers Racing recommendation: Every 6,000 miles for carbon fibre slip-ons

Warning Signs

Watch for these symptoms :

Sound changes: Your exhaust develops a “definitve raspy difference”
Visual cues: Discoloured carbon fibre, melted stickers, or actual holes
Smoke: Burning packing material may smoke from the can
Performance drop: The bike feels flat or unresponsive

“The core of the can is an extension of the pipe, and is included in the ‘tuned’ length of the pipe. Blown out packing negates this and you will lose power. Repack it and be happy!” — Tdub, racing forum

What Packing Material Should You Use?

Popular Options

Material	Source	Characteristics	User Feedback
FMF 4-stroke packing	FMF	Standard glass fibre	Works well, easy to find
Silent Sport	Specialist suppliers	Reputed to last longer	“Reputed to last longer than the FMF stuff”
Athena glass wool	Athena (S410000999001)	500x700x7mm sheet	“Just the right dimensions for beta exhaust and easy to wrap”
Bristol Core	Bristol	Claims of superiority	Forum user curious about claims
Lexx packing	Lexx	Universal	“Used the lexx on lots of bikes including my 990 which is hard on packing”

How Much Packing Do You Need?

This depends on your specific Arrow system. For a pair of Arrow cans, one forum member asked about 450g bags and was advised: “Probably best to get one pack per can and see how it goes” .

For a single can, one bag (450g) is usually sufficient, but having extra allows for proper density.

The Mesh Layer Trick

Here’s a pro tip that extends packing life dramatically:

“If the core doesn’t already have it, wrap it tight, once or twice around, with stainless window screen and safety wire it in place. It will make your packing last much longer and gives the exhaust a more defined path.” — matd, racing forum

This mesh serves two purposes :

Creates an air gap between the hot core and packing
Prevents packing from being blown out by exhaust pulses
Acts as a heat shield, reducing thermal degradation

Some Arrow systems already include this mesh. One owner noted: “I suspect that this mesh prevented the packing from being able to be blown out” .

Step-by-Step Repacking Guide

Tools and Materials You’ll Need

Drill with small bit (3-4mm) for rivet removal
Rivet gun—get a good one, “using ordinary one on mine was a nightmare to pop them”
Replacement rivets—stain steel, correct length
Packing material of your choice
Stainless steel window screen (optional but recommended)
Safety wire
Latex or vinyl gloves—”or you’ll itch for days”
Masking tape (for assembly trick)
Flat head screwdriver for gentle prying

Step 1: Remove the End Cap

Most Arrow slip-ons are assembled with rivets :

Carefully drill out the rivets holding the end cap in place
Use a drill bit slightly smaller than the rivet head
Go slow—you don’t want to enlarge the holes in the end cap
Once rivets are removed, gently separate the end cap from the can

Some Arrow systems have additional complexity: “The Arrow Exhaust has two baffle tubes which join on to each other… It can be a bit of a sod to put back together, So be careful” .

Step 2: Extract the Core and Old Packing

Slide the perforated core out of the muffler sleeve
Remove all old packing material—wear gloves, this stuff is itchy
Inspect the core for damage or excessive rust
Clean the inside of the outer sleeve thoroughly
Check the condition of any internal mesh or baffles

One owner described their horror: “80% of wool had vanished, burnt, carbonized” . You might find similar.

Step 3: Prepare the Core

If you’re using the mesh trick:

Cut stainless steel screen to wrap around the core
Wrap tightly, overlapping edges
Secure with safety wire at both ends and middle

This step “will make your packing last much longer and gives the exhaust a more defined path” .

Step 4: Apply New Packing

This is where technique matters enormously:

“Do not pack the new muffler packing too tight. That will make things loud again. There should be some “loft” in the packing when the muffler is full. That is, it should push down and spring back up.”

Packing technique:

Wrap the packing material around the core (or mesh)
Aim for even thickness all around
Don’t compress it excessively—loft is good
Secure temporarily with masking tape if needed

The masking tape trick: “wrap that with some fiber glass wrap and masking tape, nice and tight. The masking tape will burn off and stink, but hold everything together while trying to stuff it all back” .

Step 5: Reassemble

Carefully slide the wrapped core back into the outer sleeve
This is often the hardest part—”It can be a bit of a sod to put back together”
Ensure the core seats fully at both ends
Align the end cap with original holes
Install new rivets using your rivet gun

Rivet warning: “find good and strong rivet plyers, using ordinary one on mine was a nightmare to pop them” . Invest in quality tools.

Step 6: Test and Bed In

Start the bike—expect some initial smoke as tape and minor residues burn off
The exhaust may sound different initially
One owner noted after repacking: “it was quite loud to start with & then it has quietened off a bit now, It might just need a bit of time to settle in”
After a short ride, check for leaks or loose rivets

Chart: Repacking Frequency and Material Life

This chart shows typical packing degradation over time based on forum reports.

Real Owner Experiences

The Night and Day Difference

One Beta owner reported after repacking their Arrow: “best thing i have ever done on this bike… It totally changed my bike, with all time easy start whatever temp and bike cold or hot, a swiss clock with +200 rpms, and of course far less noise” .

The Racing Perspective

Racer Mark Tenn shared his expensive lesson: “I bought a fancy shmancy GPR exhaust… Two or so race weekends I noticed discoloration… Following weekend the darn carbon fiber has a big hole in it and big loss of power” .

His fix: “Al at MotoCorse does his magic and mate the remus Ti cans over the shortened GPR pipes, replaced the packing and buttoned it all up.” Result: “With the shortened cans it seems as though there may be more power. I am now able to pull on my competition down the straights where before I was not” .

The Arrow-Specific Challenge

One Arrow owner discovered their system had a sealed front section: “the front half is sealed by a plate which is spot welded into place in four locations. There is no way of getting to this part without grinding or drilling the spot welds” .

Their solution: “I may drill out the spot welds, remove the plate, repack, and rivsert the plate back into place. That way it will be removeable in the future” .

The Packing Density Lesson

A forum member shared crucial advice: “Do not pack the new muffler packing too tight. That will make things loud again. There should be some “loft” in the packing when the muffler is full” .

Comparison: Arrow Exhaust Models and Repacking Considerations

Arrow Model Type	Construction	Repacking Difficulty	Special Considerations
Carbon Fibre Slip-On	Carbon sleeve, riveted end cap	Moderate	Heat damage risk if packing fails—carbon can delaminate
Stainless Steel Slip-On	Stainless sleeve, riveted	Moderate	More forgiving, but check for rust
Full System (some models)	May have sealed front section	Higher	Some have spot-welded plates requiring drilling
Off-Road / Trials Systems	Various	Varies	May have different internal configurations
OEM Arrow (fitted to Triumph etc.)	Usually riveted	Moderate	Check if warranty implications

Common Mistakes to Avoid

1. Over-Packing

“too much and it’s loud but lasts longer, too little and it’s quieter but doesn’t last” .

The relationship between packing density and sound is counterintuitive. Too much material compresses and doesn’t absorb effectively. Too little doesn’t have enough mass to absorb sound.

2. Under-Packing

“much too little and it’s too loud and doesn’t last long” . You need enough material to do the job.

3. Ignoring the Mesh

If your Arrow has a mesh layer, preserve it. If it doesn’t, consider adding one .

4. Cheap Rivet Gun

“using ordinary one on mine was a nightmare” . Borrow or buy a quality riveter—your knuckles will thank you.

5. Rushing Reassembly

“It can be a bit of a sod to put back together, So be careful” . Take your time, ensure alignment, and don’t force anything.

6. Forgetting Gloves

“wear latex or vinyl gloves when you do the job, or you’ll itch for days” . Glass fibre itch is real and miserable.

The Mesh Debate: To Add or Not to Add?

Arguments For Mesh

Insulation: “prevents the packing coming into contact with the really hot core and burning”
Longevity: Packing on bikes with mesh “was still in great shape and was hardly detriated at all” after 60 hours
Acoustic benefit: “the little air gap there increases the silencing”

Arguments Against

Complexity: Another step in an already fiddly job
Flow concerns: Minimal, but some worry about restriction

The Verdict

One owner who experimented concluded: “it seems that by keeping the wire mesh in there I will get a lot more life out of the packing material” .

FAQ Section

1. How do I know if my Arrow exhaust needs repacking?
Listen for raspy, tinny sound—”a definitve raspy difference” . Look for discoloured carbon fibre, melted stickers, or smoke from the can . If your bike feels flat, that’s another clue.

2. How often should I repack my Arrow exhaust?
Race bikes: every 50-60 hours . Street bikes: every 6,000-10,000 miles . Some manufacturers recommend 6,000 miles for carbon fibre cans .

3. What packing material is best for Arrow exhausts?
FMF 4-stroke packing works well . Silent Sport is reputed to last longer . Athena glass wool (S410000999001) comes in convenient sheet form . Bristol Core and Lexx are also options .

4. Can I repack any Arrow exhaust?
Most Arrow slip-ons are repackable—they use riveted end caps . However, some systems have sealed sections requiring drilling . Check your specific model before starting.

5. Do I need special tools?
Drill, quality rivet gun, safety gloves, and patience . A spring puller helps with some models. Stainless steel screen if adding mesh .

6. Will repacking restore lost performance?
Yes. One owner reported their bike became “a swiss clock with +200 rpms” after repacking . Another gained power and could “pull on my competition down the straights” .

7. Is repacking difficult?
Moderately. It requires mechanical sympathy but isn’t rocket science. One challenge: “It can be a bit of a sod to put back together, So be careful” .

8. How much packing do I need?
One 450g bag per can is usually sufficient . Having extra allows for proper density.

9. Should I add stainless steel mesh?
Highly recommended. It “will make your packing last much longer” by creating an insulating air gap .

10. What if my carbon fibre is already damaged?
If the carbon has holes or severe discolouration, repacking may be too late. Some damage can be repaired by specialists , but prevention is better.

References

Have you repacked your Arrow exhaust? What bike do you ride, and what packing material worked best for you? Drop a comment below and share your experience—the good, the frustrating, and the “why didn’t I do this sooner” moments!

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