Baffles are the perforated tubes and plates inside a silencer. On many two-strokes and off-road bikes the baffle slides out and is packed with glass fibre. They quieten the exhaust and, on some bikes, also stop sparks.
What it does
The baffle breaks up the pressure pulses and slows the gas so the noise is lower. The packing absorbs sound. If the baffle carbons up or the packing burns out, the flow changes and the bike runs differently.
Signs it is worn or failing
- An engine that starts easily but will not rev on a two-stroke. See Exhaust blocked or choked with carbon.
- A much louder exhaust once the packing has burnt away.
- A rattle from a loose baffle.
- Rust holes in the outer shell, from water vapour that condenses inside. Rust through on one spot often means rust in many. See Check a silencer for rust.
When to replace it
Replace the packing when it is oily, burnt or thin. Replace the baffle if it is blocked and cannot be cleaned, rusted through or loose. Cleaning two-stroke pipes is covered in Clean a spark arrester and Decarbonise a two-stroke exhaust.
What to match when buying
- Match the silencer model and the baffle length and diameter.
- Buy fibre packing made for exhausts and fit the right quantity.
- Where off-road riding needs a spark arrester, pick one that is approved.
Fitting notes
- Let the silencer cool completely before work.
- Do not burn out carbon with a torch, and do not use caustic soda. Both can hurt the rider or ruin the pipe.
- Refit the baffle bolt or rivets firmly so it cannot rattle loose.
- Check the end-cap and the mounting. See Check exhaust mounts.