Eric, what is wrong with the 03 KX250

[troy2]

Just wondering if you have had a chance to look at one yet?According to the dyno test I have seen it is down 3 to 5 horsepower to the other bikes in it's class. Is this something that can be fixed with your porting or is it just a bad design?

Thanks,
Steve

 

[Steve47]

The 03 KX 250 is the best kawi I ever rode as far as suspension/handling/frame etc. Mine is fast but I have to agree that it's not the strongest motor. My 2000 was faster off the bottom. The 03 is OK off the bottom, great in the mid and flat on top. It's still very fast if you ride it properly. Just a lillte more power would make this bike just plain incredible.

Eric, any solutions? I bet a porting would do wonders for this baby.

 

[Steve47]

??? Update??

 

[Heat]

I have read the `03 uses the same bottom end again , does anyone know if it would be possible to use a 310 cylinder off an `00 or `01 on the `03 bottom end.

 

[the bigfella]

I just dynoed all the 03 250 motocrossers for an aussie dirt bike magazine
and the kx was down 4/5 hp on the others (8or more down on the KTM!)

gues that the Kawie boys story that the bike had all ready done 2 other magazine tests before our test could have been smoke!

Pitty the preproduction bike was a missile..............

 

[EricGorr]

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!

 

[Studboy]

Eric, So can the powervalve be fixed/modified or am I SOL on power if I buy an 03 KX250?

 

[Steve47]

Thanks Eric!

But my question is : Is your porting can make the motor a lot better? (Since it's a powervalve thing)???

Don't get me wrong. I love my 03 KX, it handle great and corners like no other KX! My 2000 motor was a bit faster but i CAN go faster on the 03! I still think that the motor could be so much better! The bike would be perfect !!

 

[Studboy]

I need more info...Eric, this is killing me!

 

[EricGorr]

I just talked to two friends of mine that spend a lot of dyno and riding time on the KX250s, Jesse Williams from Motorwerx a pipe builder from Port Washington WI. and Tom Zant the head mechanic at The Great Escape in Crystal Lake IL. Tom is a well-rounded mechanic and tuner and has spent considerable time trying to smooth the transition of the valve in the full open position.
Bottom line is the KX is going to struggle to keep up to the others on top end, even with considerable porting.

 

[Steve47]

Just switched the stock 52 pilot for a 55. Wow what a difference, the bike pulled stronger off the bottom. A lot stronger!

 

[troy2]

I am keeping my 2000 KX250 then. Just ordered an EFM No-Stall clutch for it. Between Eric's porting, the suspension re-valve and now the clutch it should be close to perfect for the woods.

Steve

 

[Studboy]

Eric, so can the bike be made to be competitive with porting/vforce2? Or is it always going to be short on power? I prefer a lower rpm powerband anyways over a high RPM screamer on a 250. How will the stock 03 KX compare to my 94 KX250 with .080 overbore, wiseco piston and rings (fresh), boyeson power reeds, pro-circuit pipe and silencer? I know that motor is pretty much stock, but I have beaten quite a few '00 '01 and '02 250s at the sand dunes with it!
Sorry so long, I have a lot of questions to ask before I spend $5,500 on a new bike!

 

[Wakisashi]

anyone had an `03 cylinder off the bike? Is there enough cylinder wall for a vet class bore job ? 285cc maybe

 

[EricGorr]

The KX cylinder is a big sturdy bugger, you can punch that thing out to 74mm 310ccc without any structural concerns.

 

[Studboy]

Eric, another question, will the cylinder off an older KX fit the 03? That could solve a lot of problems. I'm sorry about so many questions, I know you're busy!

 

[Studboy]

Bump

 

[Studboy]

Sorry guys, I hate to keep bumping this up, but I need to know. Bottom Line, Can this engine be successfully modified, and will it be competitive? I don't care if it doesn't scream at 10,000 RPMs.

 

[Steve47]

StudBoy, the engine can be competitive no doubt! Fitting a old cylinder may be tough, the 03 head is mounted from the back so you'll need the 03 head for sure. The cylinder may fit but will the head fit on the cylinder?

 

[Studboy]

Have you raced your 03 against any other bikes or is that just your opinion? Is the overrev really as bad as everybody says? You do make an interesting point. I imagine that you could just flip the older head around...maybe not though.

 

[Steve47]

I pulled 2 holeshot against a full 40 bikes gate at the GoldCup series in Fla. All my other starts were in the top 5. SO NO It's not that bad, the bike is competitive, you just need to ride a bit harder out of corner but the frame let you do that easily.

 

[marcusgunby]

I dont beleive any 250 2 stroke made doesnt have the power to win a race-corner speed is far more important-and from what i have read the KX corners very well.I seem to remember in 1992 Jamie Dobb won a world GP on a KX250 that was esentially std-including std suspension.

 

[Studboy]

A new update... so I was reading the other day in a magazine and Pro-Circuit is claiming with a little loss in low end (basically a trade) that they are getting at 8500 RPM +3 HP 9000 RPM +11 HP (Over stock) 9500 RPM +14 over stock on the 03 KX250. They say that under 7300 RPM the Pro-Circuit makes a little less HP. So, effectively, they are saying that just by their pipe you are changing the effective overrev range from 8200 to 9500 RPMs. Considering Eric's post about the flawed powervalve design how is this possible? Enlighten me.

"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.

 

[bigred455]

If you can match a pipe for the blow down time of the exhaust and tranfers t/a sure I think it is possible.Are they talking plus 3 hp at 8500 on the rear wheel or crank,I bet they just said 3 hp ,Which in my mind is at the crank,The way mx action is.Stll 2.5 at the rear is a nice gain.I wonder how much is lost at the bottom.

 

[Studboy]

They didn't say R.W.H.P. or Crank H.P. (Doesn't surprise me.) But I still don't see how they could raise the effective RPM range another 1300 R.P.M. due to what Eric said it was being limited by a flawed P.V. design.