FMF too loud

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?


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

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

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