Animated service guide
Dirt Bike Silencer Repack, Animated
The packing in your silencer is a consumable. Its fibers blow out the back a little every ride until the bike gets louder and its power changes. KTM’s manual says the silencer “burns out.” Repacking is cheap and takes under an hour, and it is the right time to look the pipe over for dents, cracks and leaks.
The animated guide loads here. Every step is also written out below.
Looking for the full article? How To Repack A Dirt Bike Silencer covers this job in depth. This page is the animated, step-by-step version used in the MotoMind app.
Before You Start
Tools
- Sockets or bits for the mount and end screws
- Torque wrench that reads low (5 to 30 Nm)
- Drill and rivet gun for riveted cans
- Gloves and a dust mask
- Rubber mallet
Parts And Supplies
- Silencer packing made for your can (two-stroke or four-stroke)
- End cap O-ring if it is flat or torn
- Thread locker if your manual calls for it
- Rivets for riveted cans
Safety
- Let the exhaust cool fully. It stays hot long after the engine stops.
- Glass fiber packing itches and sheds dust. Wear gloves and a mask and work outside.
Step By Step
Take the silencer off
With the exhaust cold, remove the silencer mount screws and their washers. Twist and pull the silencer straight back off the pipe at the sleeve. A rubber mallet helps if it is stuck.
- Socket
- Rubber mallet
Silencer mount screws Bike Spec Source KTM / Husqvarna / GASGAS 10 Nm (7.4 lbf ft) M6 screws. KTM 250/300 SX/XC 2024 OM PDF p. 70; KTM 250 SX-F 2024 OM PDF p. 159 Yamaha YZ250F / YZ450F 30 Nm (22 lb ft) M8 silencer bolts, front and rear. Yamaha YZ250F 2026 OSM PDF p. 65; YZ450F 2026 OSM PDF p. 63 Use the silencer mount torque from your manual.
Check the pipe while it’s off
Look over the header and pipe. Dents change the inside shape and soften the power on a two-stroke. Look for cracks at welds and mount tabs, black soot at joints, which means a leak, and tired springs or flat O-rings at the cylinder.
- Flashlight
Careful. KTM lists a leaky or deformed exhaust as a cause of low power. Fix leaks before you blame jetting.
Shop tip. A badly dented two-stroke pipe is usually replaced, not fixed. Small dings matter less than a flat spot on the belly, but any change in shape alters the tune.
Remove the end cap
Take out the end screws around the back of the silencer and pull the end cap. If your can is riveted, drill the rivet heads off with a bit just bigger than the rivet stem.
- Hex bit
- Drill (riveted cans)
Pull the inner tube
Slide the perforated inner tube out of the outer tube, packing and all. On KTM two-strokes it comes out with its O-ring. Mark which way it faces so it goes back the same way.
- Gloves
Strip and clean it
Peel off all the old packing. Clean the inner tube and the inside of the outer tube, and check the tube for cracks around the holes. A cracked inner tube or a split outer shell needs a new part, not just packing.
- Wire brush
- Gloves
Wrap the new packing
Wrap the new packing evenly along the inner tube, or slide on a pre-formed sleeve. Fill the space firmly but not crushed, because packing stuffed too tight can’t do its job. Some four-stroke cans also have packing in the end cap; KTM’s SX-F does.
- Packing
- Tape (optional)
Shop tip. A wrap of masking tape holds loose packing while you slide the outer tube on. It burns away on the first ride.
O-ring on, tube in
Check the end cap O-ring and replace it if it is flat or torn. Slide the outer tube back over the packed inner tube in the same direction it came out. Twist gently so the packing doesn’t bunch up.
- O-ring
Screws in and torqued
Fit the end screws by hand first so they don’t cross-thread, then torque them to spec in a crisscross pattern. Riveted cans get new rivets as the maker specifies.
- Torque wrench
Silencer end screws Bike Spec Source KTM / Husqvarna / GASGAS 7 Nm (5.2 lbf ft) M5 screws. KTM 250/300 SX/XC 2024 OM PDF p. 71; KTM 250 SX-F 2024 OM PDF p. 82 Yamaha YZ250F 8 Nm, thread locker M5 silencer body bolts (except EUR models). Yamaha YZ250F 2026 OSM PDF p. 65 Use the end cap screw torque from your manual. These are small screws in thin aluminum, so go gently.
Careful. Small M5 screws strip easily in aluminum. Use a torque wrench that reads accurately at low values.
Refit and listen
Slide the silencer back on the pipe, fit the mount screws and torque them. Start the bike and listen for leaks at the joints. It should sound noticeably quieter than before. Wash with the outlet plugged, since water in the can causes rust and hard starting.
- Torque wrench
When to repack Bike Spec Source KTM / Husqvarna / GASGAS SX, SX-F, XC, XC-F (race) Every 45 h KTM 250/300 SX/XC 2024 OM PDF p. 36; KTM 250 SX-F 2024 OM PDF p. 42 (stock silencer) Yamaha YZ250F / YZ450F (race) When louder or slower Replace the fiber when the sound gets louder or performance drops. Yamaha YZ250F and YZ450F 2026 OSM PDF p. 93 Pro Circuit aftermarket cans Every 10 to 15 h Pro Circuit FAQ; desert riders sooner KTM XC-W / EXC, Husqvarna TE 2-stroke (enduro) Every 90 h Stock silencer. KTM 2026 XC-W OM PDF p. 55; Husqvarna TE 250/300 2026 OM PDF p. 55 KTM 450 / 500 EXC-F, XCF-W (enduro) Every 45 h Stock silencer. KTM 450 XCF-W / EXC-F / 500 EXC-F 2025 OM PDF p. 54 Honda’s CRF-R manual lists no packing interval; it says to inspect the exhaust pipe and muffler every race. Repack when it gets louder or loses snap.
Sources
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