KX250 vs. KX250f two-stroke conversion

[KevinTwoStk]

Reading the build threads by jbersano and ZETTNORCAL has intrigued me.

Right now, I have a KX125, but at some point I'd like to add a KX250 two-stroke to the stable.

I've got mad respect for those who ride KX500's (along with all other Open-class two-strokes) but I'll stick to 125's and 250's.

My bike(s) will be used for play riding in SoCal and hopefully some Big6 GP's.

My questions:

--Would a production '03-'04 KX250 be just as good as a two-stroke converted '04-'05 KX250f?

--Is the 250f chassis better than the two-stroke chassis or are they hard to tell apart?

--Is the 250f chassis narrower than the two-stroke chassis?


Thanks for your feedback, and thanks for the great build threads!

 

[Motorrad]

The last of the two strokes were pretty awesome..

Id get one.. get the suspension revalved for you...

and go ride..

[don46]

First,

If I was going to purchase a 03-04 250, I'd spring for the 05-06 or 07 version, the motor is differnet 03-04 is more like the 99-02 version in an upgraded chassis.

second,

If I had a newer 250 2t I wouldn't put it in a steel 250f frame, suspensions are very similar.

I still have a 06 250 steelie, and I built an 06 Aluminum framed 250, other than the bling factor there wasn't much difference, although I do like the Showa suspension.

BTW, I sold the AL framed bike.

[KevinTwoStk]

Thanks guys!

Yeah, it sounds like the best bet is to find a good KX250 two-stroke and go ride it.

I've read some negative things about the handling of the '05-'07 KX250---even here on KXRiders. There was a review of the '07 KX250 in MXA which included the sentence "In our opionion, this is a flawed chassis." Those are pretty strong words!

I think my best bet is to get an '03-'04 model and go from there.

Thanks again,

Kevin

[The Flyin Hawaiian]

+1 on the 03-04 models. I currently have them all. I have alot of time racing enduros the 03 and 04s. My wife raced a 07 for one season then parked it and jumped back on her good old 03. We rebuilt her 03 using some parts from a 04. We used the 04 head for more compresion and more lowend (something the 03 lacks), the CDI to smooth the power out and probably the biggest differance was made when we swapped the 03 powervalve governor spring for a stiffer 04 spring. The 03 has a weak spring that allows the powervalves to open too early causing a very noticeable flat spot off the bottom. The 04 spring cures it. The suspension on the 03 works better for offroad due to the open chamber, non bladder forks and the rear linkage arrangement. When properly valved and sprung , the 03 will soak the small stuff (roots, rocks etc) very well. The 04 also works well for offroad. It puts out good lowend with a smooth transition into the mid and decent top end. I have a rare Enduro Engineering pipe on mine (the 03 runs a FMF Gnarly) that really wakes it up. It gives up nothing to a 07 in a drag race. They are pretty much even. The suspension on the 04 seems to work better in the high speed stuff than the 03. This is due more to linkage arrangement and to a lesser extent, the forks. But, even revalved, the 04 suspension doesnt soak up the roots and rocks quite as well as the 03. Its not bad but I feel the small stuff a bit more. Both use WER steering dampers and a WER revalve.
 Now to the 07. As I said earlier, my wife raced it and complained about a vague feeling from the front end. She just couldnt trust it to stay planted. It would both knife and wash the front end. The power is strong but it is weak in the bottom end with a massive mid hit and good topend. The lack of bottom makes the mid feel overly strong. Its fun for a little while but can be a handfull in tight and technical terrain. Im going to tinker with it this season and see if I can get it to handle better and also get some more bottom out of it. Keep in mind that our bikes are set up for tight eastern riding.  

[stevea100m]

Hey flyin my dad has an 06 that is pretty much is the same as 07. We went and changed the pipe to the FMF SST pipe and put an optional factory flywheel weight on it i think it was a 5.2 and it made the bike so much more easy to ride. The front end is still pretty stiff though even after being revalved so i know what your talking about. It is an awesome mx bike though just not so much in the woods but if not for a stuck float at the jackpine national enduro last year the guy ridin it would have had a top 10 so it can be done

[Openclass]

Do you know what the difference is between the 06 and the 07? Is this the same front end setup for both bikes. I have an 02 but I have rode my uncle's 06. I thought it was a little smoother power with a little lighter front end feel.

[The Flyin Hawaiian]

The 06 and 07 are pretty much the same bike. I did read somewhere that the piston was changed between the 2 years. My 07 has a Gnarly and a FMF Q silencer along with a set of Boyesen reeds. Also has a 11oz Steahly FWW. It is much better than stock but still lacks the off idle pull that the 04 has.  The vague feeling front end comes from the steering head angle. It was pulled in slightly in 06. Causing the knifing. The 05 is supposed to handle better. We also ran revalved 04 forks so stiffness isnt the issue. I know it can win, its just that we are more comfortable with the older chassis and motor.

[don46]

The 05 motor is pretty much the same as the 06 and 07. We run Pro circuit on ours, no  fww although I do have one and could. My son rode his mostly on the MX track when it was new, now he rides it playriding and cross country, front end is not an issue for him. He was a national caliber MX rider and a AA cross country rider, the 06 was by far his favorite two stroke, well almost but thats another story. What it really comes down to is personal preference, how the bike is set up and what kind of riding you do. I think the 2012 450 wil work cross country although in tight conditions it may be too much.

[KXDINO]

My 2 cents worth, the 03-04 were better handling than 05 -08 bike.

05-08 bikes share the same frame 32160 - 0104 - 458 and have a too steep head angle of 26 degree.

They would tuck or wash out half way around a corner, so you would use your leg to prop it up, especially on slippey and lose surfaces.

KXDINO

[KevinTwoStk]

It looks like this place could modify head angles to suit:

http://www.wascoframe.com/index.html

MXA is on Dino's wavelength: The same MXA article I referred to earlier also described the '07 KX250 turning technique as "stomp and turn." You get halfway through the turn and you keep from falling over by stomping your foot on the ground, then complete the turn.

It sounds like a head angle mod might be the best way to fix the handling.

Other than that, the '05-'08 sounds like a great bike. The '03-'04 still sounds better out of the box.