February 2010 Dirt Bike has an article on KTM Power Valve Tuning. Now I'm really confused. I want as much low end as possible, with a smooth power delivery. For years, I have been running the red spring. If I understand this article correctly, it is saying that's all wrong. For a "broader, or smoother" powerband use the GREEN.
Which is correct?

God bless you figuring out the PV...

We have guys go full circle... It is so rider dependent.. It also depends on Jetting and motor set up (compression, squish, X dimension).

Once we dial in the motor and get Jetting right on then the PV setting seems to make sense, and we end up with the red spring 9 out of 10 times.

I have not read the article so I am no help there..

I saw the same write-up and don't know if I agree with their conclusions. The article's basic premise was that an early opening PV = an aggressive hit. There is more to it than that, but it takes a little more thought than what they covered. Each of the springs will have different rpms when they allow the PV to begin to open (somewhere between 5500-6500rpm); a light spring equals less resistance to overcome. If the power valve opens sooner, does it necessarily mean that the powerband becomes abrupt? One could argue that a more gradual opening that starts earlier and closely follows engine rpm can yield a more linear powerband. A high rpm activated PV spring that opens later (green) may not be the best choice for everyone looking for smooth power. Their commentary on the external adjustment screw appears to be reversed and contradicts their earlier logic on the spring choice. As Mike stated, most riders will wind up using the red spring and adjusting the external screw to suit their riding style - many find that flush with the case works for them. Springs are $3 and take 2 minutes to change, so see what works best for you.

Very well put Dan. I like the red tured in just past flush on 09 300xcw. I ride the bike a gear high and lug it around like a tractior and the extra power of the red seems to help give it more power in a higher gear. When you feel frisky you can down shift or rev it out and hold on. Lets you control the power like it should be, instead of the motor being down on power its ready when needed.

Thanks everyone. If anything, I am encouraged here to experiment.
As Mike S. said, I am often impressed by how much of all this "overlaps". Jetting, timing, pipe configuration, PV settings, pre-mix ratios, plug heat range, squish band, and octane levels all play a part in "tuning". Regarding dimension "X", this year I actually went tighter in the squish hoping for more low-end. I have dimension "X" set at +0.0001mm (spec is 0.000 to -0.004). It was by de-fault: I couldn't get it exact with the limited configuration of base gaskets. This should really BOIL now. I might be headed for "ping city".

what exactly done to the head and how much

Bike is all back together. I know Mike S. does SUPER work, and knows these machines VERY well, I'm just not that fast that I need his "special touch". When I can ride as fast as his son, I'll think differently.

My 05 came through with the yellow installed from the factory,the service bulletin that came with the owners manual says to install the green spring for an even smoother power delivery.The red spring is for a more aggressive power delivery.I believe the artical number is 3.211.61 that states this.I guess that this is all relative to the condition of the motor,how well tuned it is,the type of pipe your using,quality of gas ect.

I found this article in an old edition of Dirt Bike, I think it makes more sense than the article in the recent Dirt Rider

Bon appetite

http://gpsroutebuilder.com/Documents/PowerValve.pdf