Originally Posted by yama426rider
so would a fmf factory 4.1 for a 450 fit my 426 and if so how loud are they?
You can fudge the FMF system into place on the 426, whether it's a full system, or a slip-on. The muffler isn't welded to the midpipe, and it mounts with a band clamp that can be positioned anywhere. The headers on the two bikes are the same, so as long as the 450 it came from is an '05 or older, the only point where you might have to do some filing is at the midpipe mount on the frame.
I'll guess that they run around 98-99db with good packing. Not great, but not nearly obnoxious, either.
I'm needing a new silencer for the ol wr426. I'd like to install the Ti Powercore but they don't make it for 426's and it has a fixed mounting bracket. Should I take a chance see if it will fit or order the old style powercore IV.