FMF too loud

3 replies to this topic
  • beairmo

Posted September 08, 2013 - 07:13 AM


I bought my 2009 WR450 used and it was already fully uncorked and has FMF Factory 4.1 Titanium with power bomb header. I just repacked it and no leaks.

I am not happy with how loud the bike is and the popping on decel. I am considering a different muffler and possibly the FMF Q4 Ti.

Can anyone tell me how much the Q4 will quiet the bike down and what else to expect over the 4.1?


  • Krannie McKranface

Posted September 08, 2013 - 08:05 AM


It's about 3db quieter overall, and it's about 10db quieter at idle.

All FMF's have a loud 'peak' idle tone because the core is short and large in diameter.


You need to make sure you follow a special re-packing procedure:


Wire-brush clean the perforated core to remove carbon

Wrap the core with 00 grade steel wool 3/8" thick

Use FMF solid repacking wool (not the loose stuff) wrapped just tight enough to be larger than the can by about 3/8", held in place with masking tape

Compress it as you go to get it to fit into the can

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  • five_pointe_o

Posted September 08, 2013 - 08:40 AM


Sounds like you're lean with the jetting if it pops on decel. Fmf should sell a quiet core that lowers the dB level a bit for your factory 4.1 exhaust, it would be cheaper than buying a new muffler/system

  • KennyMc

Posted September 08, 2013 - 09:03 PM


Like the previous poster mentioned. Might try this first.



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