2006 YZ 250 jetting?

At 2,500', you are probably running slightly rich. Have you taken any plug readings? Are you getting a lot of silencer spooge or fouling plugs? Those YZ's are borderline on pump gas, so being slightly rich is probably a good thing.

I hope this doesn't turn vital either.

The process of proper jetting is testing. Always with a controlled variable. Like how scientists do it, Bro !

It's not enough to say... "while on stand hold the throttle at a specific RPM and position and listen for these vague engine characteristics. Then precisely adjust this particular circuit." This message from the other thread were only intended as a solid foundation to play around with. Jetting circuits are not independent from each other, rather they work together to deliver the optimum air-fuel ratio.

I'm willing to bet PC jetting suggestion are in the ballpark but each bike has too many variables for one unconditionally best setup. No one can tell you what the best set up for you without tuning first hand. The rider and track conditions are two of the most under looked aspects of jet tuning.

All you gotta do is buy several jets that are close to your current specs and start playing around at the track. OEM main and pilot jets can be purchased from Motosport.com for under $4.00/piece through their current OEM discount. Pro-X main and pilots can be found even cheaper. Once you learn how to change a jet and what you like, you will enjoy changing a jet trackside to fine tune your motor.

In leu of seeking any further advice from the vitals, I suggest reading something worthwhile in the article posted below and let the speculative jetting opinions stay in the other thread.

http://twostrokemotocross.com/2009/12/carburetor-theory-and-tuning/

That's PC's sea level jetting. It's good up to about 1,500'. I would test dropping the needle one position and one size smaller main. Just be sure to listen for detonation when you start leaning it out.

I agree with CamP, but in addition, you will want to mix some race gas in the mix. At least 1 gallon to 2 gallons premium pump. The YZ's like to detonate on pump gas, especially if you are riding in any kind of high load (sand) situation.

To move the hit slightly higher in the powerband, put a Boyesen RAD valve in, and lose the stock reed block spacer. You can try losing the spacer with the stock reed block too. Also, which PC silencer are you running? Run the long one (304) to get power up top.