I just bought the BMP exhaust for my YZ426. Check out http://www.bmp.motox.org/. It's a nice little kit. It was designed to fit YZ400s. Bill (from BMP) talked to a Yamaha contact and they said nothing changed on the exhaust for the YZ426, but Bill and I found out otherwise. The pipe is a little larger in diameter. I had to take the base plate that comes in BMPs kit to a machine shop and have them bore it out to 1 29/32 (exact fit, you know). Other than that, the kit installs real easy. Just drill out the rivets on the original end cap and install the new end cap.

So for $129 you get a SA. With 8 plates it is quieter. Mostly takes the edge off the sharp sound when you pop the throttle. With less rings it definitely gets quieter. Not sure what it does to the power band yet. If you're looking for an inexpensive exhaust alternative, I'd recommend BMP.



------------------

Finally, had a chance to check out how the BMP exhaust effects my power. With eight plates (which comes in the kit) it definitaly cut the power (and the noise). For me, it actually made it a better bike for woods riding because the power came on a lot slower and smoother, but out on the track I really missed that snappy, in-your-face power.

So I had BMP send me 4 more discs. Running 12 plates returned much of the power I had lost. Second and third gear wheelies are back! The sound level is still a bit quieter than stock end cap, but not much. I'm going to put a few more plates on to bump it up to 15 plates. I expect this will give me back all my power. Then for $129 I basically have an exhaust system I can quiet down for the woods and open up for the track. Not bad in my book!

I agree. I have one as well and it is great. It is adjustable (tunable) for what ever you are doing (MX or trail riding) I would recommend it as well. This had a write up in a dirt bike magazine a while back, they thought it was a good idea too. The price is right and it has held up pretty well. A friend (with friends like this who needs enemies) over jumped a table top and landed on me and my bike. It caught the silencer. It bent the cap and a few plates. Replacement parts were cheap from Bills and I was on my way within a few days It still worked while smashed. It was a hard hit and I think it held up very well. If you have some nuts tacked on to your stock endcap you can switch them back and forth, great idea. Anyway, I would recommend it.