Who here has ran both a Fatty & Gnarly on there bike? I'm in the market for a new pipe on my 03 KX 250. I'm thinking of going with the Gnarly for the first time. I've had both the Pro Circuit Works &  FMF Fatty on this bike and like both, but I'm still looking for more bottom end. My question is just how much bottom end is gained over a Fatty & how much top end is sacrificed? I'm thinking the Gnarly may be for me. I ride 50/50 woods/track & I'm not one to keep the bike wound up all the time, even on the track.

I've run both and there is a difference no doubt.  The gnarly will give you good boost off the bottom.  Any loss of top end can be mitigated with a spark arrestor (FMF Q or the standard). The other added benefit of the gnarly is the tougher/thicker gauge constuction.  Of course, if the top end isn't fresh than your wasting your time.

One other thing you might want to try before you drop serious coin on the pipe is slightly advance the timing.  BTW, are you running the powervalve shim that FMF sent with the pipe?  Do a search on it, I believe it livens up the mid-range a bit sooner (maybe not what you want).

Good luck!

I finally got a chance to take the bike apart to powder coat the frame & put on new plastic. While I was at it, I went for the Gnarly. I haven't had a chance to ride it yet, still waiting on the chain to come in. I also went with a 50 tooth sprocket. I can't wait to get a ride in and see what difference it makes.

I haven't done the power valve shim. How much & what kind of difference should it make? I think that I'm going to ride it like it is for a few rides to get a real feel of things, then try the shim.

The shim mod is on the Candian Team Green site in pdf form.