FMF Factory 4.1 Slip On

I just finished installing it and fired it up for the first time. Sounds awesome but it's a bit louder than I thought it would be. Not sure how much quiter it is with spark arrestor installed but will find out soon. Couldn't let it run long since the header started to glow. Will have more feedback on results once it has been re-jetted. Very easy to install and looks great!

Just got it back and rode it for the first time. Still love the looks and it sounds awesome. I haven't tried it with the spark arrestor in it yet but I'm assuming that it will quiet it down some.

i had the spark arrestor in my yz450 and took it out it made much more overrev pulled further in each gear its not that loud

you can hear it on utube yamaha yz450f power 2011 model

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