Eric, what is wrong with the 03 KX250

[jaguar]

I think Eric's already answered all your questions (except whether or not an older cylinder/head would fit).
The bike is super competitive as long as you know how to use its powerband. If you only know how to scream a bike then buy a screamer.

 

[Barker]

I think Eric's already answered all your questions (except whether or not an older cylinder/head would fit).
The bike is super competitive as long as you know how to use its powerband. If you only know how to scream a bike then buy a screamer.

I toyed around with the powervalve last weekend on the 03 250 while doing the top end. It looks like the 05 and the 03 mid valve are still the same, but they have changed the side valves to a barrel type in the 05. What (one?) of the problems looks like on the 03 side valves is they don't recess completely back into the cylinder and almost block half of the port cast into the cylinder. You can index the valve to where it does recess completely, but then the exhaust chamber ports are not opened up, plus they wouldn't completely seal when closed. It would be hard to grind the valves to make the geometry correct, and the only fix I saw was to grind the opening into the chambers to match the valves if they were run indexed from the standard position. Problem there is there is only a cover on one side to access the chamber opening, and the aformentioned sealing when in the closed position. Terrible engineering, worse then my explanation :)

 

[fatherturtle]

glad to see this post, I have been waiting to see if someone would try to figure out the powervalve on the 03. I am pretty disapointed with this motor. Granted yes you can still be competitive with this engine but man I don't like having to work so had to keep it in the power band. I don't want to buy a PC pipe and have to stay above 7000rpm. I want something that is going to have a little more kick. If you find the solution please let me know.

 

[bclapham]

"If you are willing to give up some of the KX's healthy low-end burst, the Pro Circuit Works pipe will reward you with three more horsepower at peak. From 8200 RPM on (which is exactly where the stock pipe begins to lose horsepower) the Pro Circuit pipe starts to romp. At 8500 RPM, the Pro Circuit pipe makes three more horsepower. At 9000 RPM, it makes 11 more horsepower. At 9500 RPM, it makes 14 more horsepower. Plain and simple the Pro Circuit pipe trades low end for top end." That is exactly quoted from the Jan. 2003 MXA magazine, pg. 156.

Somehow I smell snake oil, but I could be wrong.

14HP, they should lay off the pipe. :coocoo:

 

[Studboy]

And what "pipe" would you be talking about there bruce? :yikes: :rotfl:

 

[Rcannon]

Here is the part I dont buy about this. Kawasaki is a giant company. Would they do the R & D on the stock exhaust pipe and leave 14 hp sitting on the table? I dont believe it.

At least the Pro Circuit pipes fit.

 

[dirt bike dave]

Here is the part I dont buy about this. Kawasaki is a giant company. Would they do the R & D on the stock exhaust pipe and leave 14 hp sitting on the table? I dont believe it.

The way I read the test quote, it is not a difference of 14 peak hp. Instead, it is a 14 hp difference at one specific rpm point, and that rpm point (9,500 rpm) is way past the range the stocker is designed to work in.

Sounds plausible to me, especially you are comparing a high rpm pipe to a stock pipe that is designed for low-end and is known to have no over-rev.

 

[Barker]

glad to see this post, I have been waiting to see if someone would try to figure out the powervalve on the 03. I am pretty disapointed with this motor. Granted yes you can still be competitive with this engine but man I don't like having to work so had to keep it in the power band. I don't want to buy a PC pipe and have to stay above 7000rpm. I want something that is going to have a little more kick. If you find the solution please let me know.

Mine is a Canadian bike, paid around $4300 new.
I'm into vintage Kawasakis, and thought why not.
The Gnarly pipe and V-Force reeds wake up the bottom end (worth the $300 bucks), very rideable, still not a match for my 99 CR250 motor setup the same way. Fun none the less, great for trail or entry level mx (with suspension work, the chassis is pretty decent). Would imagine if someone is/was doing well on arenacross type tracks was because of it's "under abundance" of power making it easier for the chassis to hook up. I also have an SST pipe for it, less bottom than the Gnarly, lets it rev way out there, but really not much more HP over stock. With the powervalve setup like it is, the flat spot at mid range is going to always be there (FMF washer or not, it's a mod they recommend). If it's still around for another rebuild, the EG big bore sounds like the way to go. More info at http://www.teamgreennews.ca/techside.html

 

[Barker]

I'll take a SWAG at this one (Scientific Wild Ass Guess) Its the center exhaust valve. I think that the leading edge produces some type of shock wave that hinders the exhaust flow. They introduced this new sliding system in 2002 and the top end power went away on the 125 and 250 but the port timing hadn't changed from the previous year. The KX250 suffers from chronic problems with the 1993-2001 articulated valve, with breakage and wear of the pivot pin. The sliding valve cures that malady but it obviously doesn't work. I hope Kaw switches over to the plunger type exhaust valve system in the future. I wish they'd just bring back the 1996 model, that was the best KX250 ever!

The inner leading edge of the center exhaust valve, stop, and the roof of the cylinder exhaust port while the valve is just beginning lift does look pretty strange. Makes me want to grind on it.