falling off on top end

What does "some jetting" mean? There are two types of jetting; correct jetting and incorrect jetting. It is possible that your main jet is too small. This will cause the bike to fall flat on its face. Check the FAQ for jetting advise.

Is this a new condition or is it something that you never had the opportunity to experience?

Sounds to me like you ran out of gearing and rpm's. My bike does that too, I reach a certain speed and can go no faster, even if I rev the heck out of it. Its called overrev i guess, and i have it.

The Gnarly pipe is designed to produce mainly low to mid power, at the expense of some top. Also, the port timing and powervalve arn't exactly designed to produce high rpm power. Most KDX's tend to fall off the power quick and hard in stock form, and the Gnarly pipe isn't going to be helping top end too much. Search the site for different articles on the different pipes for the KDX, and how they affect power. Lots of good info out there.

rv6: 'some jetting' ha! ;)

qwazi: The 200 is by no means a track bike. That said, the 'falling off' could be either endemic to the kdx clan, or indicative of a problem .....depending on the nature of the falling.

Jetting is a big deal. A Big Fat Big Deal. With a couple of misadjustments to jetting on my bike I can make it 'fall off' on the top. I've never run it too lean, so I can't tell you from personal experience on this bike what that actually feels like. But, based on other 2-strokers I've had (and common sense) I can tell you that too lean will certainly lead to a 'falling off'...about one nanosecond before your engine seizes up tight.

Too rich will do it, too.

Which brings us around to rv6's comment. Recall goldilocks and the three bears? That's a fairy tale based on the basics of 2-stroke jetting! (you learn something every day, huh?)

There's too fat, too thin...and j-u-s-t right!

Even after getting the jetting spot on, there are additional (bolt on) mods that will help the top end of the 200. The -30 pipe for one (as atc already said), a reed set intended to go fast..as the DFII (set to hi tension) is.

Of course, after you make such changes you will need to jet all over again!

But...the 200 will never be a real track bike.

re: Well is there not really any concern for the others?

Because in a track situation, you don't use 'em! It's largely WOFT ATT.

Who on an mx-track cares about off-idle response to 3/8-1/2 throttle?

Who in the woods doesn't?

Have fun!