FMF Factory4

Anyone running a fmf factory4 silencer on your yz 450? If so hows the power compared to stock and did you have to rejet?

In my experience with the FMF pipes I got more of a gain out of the header than the muffler. I bent my stocker and put the PB on as a replacement. Nice gain. I put the muffler on to match later with very little gain. Get the header first.

I've got the full Factory 4 system on my '04, and I would definately say that the power is increased throughout the powerband, but to me the most significant difference is from the mid through the top. I am able to pull gears much longer, without shifting as much. Of course, since I have the header, it is impossible to tell where the biggest change was gained, but I'm sure the muffler/midpipe play a big part. By the way, a jet kit was included, but I am trying to see how close I can leave it to stock, so I am still playing with the fuel screw. I'd be interested in hearing what others are running for jetting with this pipe.

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