Jetting Questions:

Hey Folks got some jetting questions for ya and if anyone can help I'd appreciate it. First of all I have a 2000 WR400F that's YZ timed, Grey Wire is cut, and have a Thunder Alley Pipe. I also live in Reno NV and ride at about 4500 to 7500+ feet most of the time. The problem I'm having is that the power just seems to flatten out up top. Cannot get close to hitting the rev limiter in 5th gear. Couldn't do it with the stock pipe either. 4th gear bounces of the limiter pretty easily, but still feels pretty flat towards to upper reaches of the rpm range. The power down low to mid is great. Pulls hard right of idle, through corners, etc. It just seams to flatten out mid to top end. Also, the bike always starts 1st kick cold and never starts with it hot without using the hot start.

Right now I've got a 170 main, 48 pilot, and a OBDRS needle in the #3 position. The plug does get a bit black but not too wet & has never fowled. When I got the Thunder Alley pipe, Bob (the owner of the company) told me that if the bike felt flat anywhere, to just increase the size of the main jet one size. I did go up to a 172 main & didn't really feel any changes.

I'm wondering if my jetting is so far off or where to even start. I don't want to start playing with everything just to screw it all up. Maybe its just me and its all fine as is and I'm looking for something that's not gonna happen. I don't know. Just wish I could top the bike out, pick up more speed, and leave my buddies DRZ in the dust. Right now it's faster than mine.

PS, as if this isn't long enough, I've had my bike up to 88 mph using a GPS and my friends DRZ has been up to 92 on the same stretch. I've been told that my WR should be able to leave ANY DRZ in the dust in a drag race. Just pisses me off when he's inching away & there's nothing I can do about it.

If you stop accelerating on top, just kind of run out of juice, the main is too rich. Actually, it looks like you're jetted way too rich all the way around, especially at your altitude. Look at the jetting in my signature. It should work for you, too.

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