Frame question for a 250af build

[funke93]

Hey guys been quite a while since I last posted... Sold my kx250 roller on here and started a different build... A zx10r that loved taking my money more then any girlfriend I've ever had! Now that I am finished up this bike and getting ready to sell to help pay for schooling, I've gotten an itch and this particular itch involves a partially complete bottom end for a 99-02 kx250 that's been in my basement since the fall of Rome. Now this would be my third kawi and Ive always wanted a AF built bike that I have done myself. Now question for you guys is the 450f or 250f a better platform to start on and why which years have the most interchangability? 06-11 kx450f I've been told? But also heard the 06 has stink bug suspension. I've been lurking for quite some time reading up on all the 250af builds just figured I'd finally spill my guts. (:

[don46]

I would use the 250f chassis for a 250, the cradle area is a bit more compact on the 250f. and I would use the 250f Showa components on either frame. The last 500 af I built I used the 450 frame and the 250 suspension, in fact many serious racers are doing that, they bolt right up, gotta have the triple clamps as well for the 250f. I did one of those builds a few years ago for my wife, I used a 06 motor, realized it was to much for her so I peddled it. I do think the 01 motor is a bit tamer and easier to ride so it should be good

[funke93]

Hey don! Thanks for the response, I have read some of your posts on suspension remember reading not to go with the kyb's and use the showa's instead. The Showa forks are on the 06 to what year and only the 250f forks right? I heard the 06 450f suspension isn't that great are those Showa units as well? Why wouldn't you want the extra space that comes with the 450f frame? Are there and issues with the gas tank to spark plug spacing when using the 250f frame. Also which year 250f frame should I look for, I'm not the type the always believes newer is better. Also since I'm saving to leave for school and finish up my degree away from home starting next semester this build will take awhile. Also the kx250 motor I'm going to start building I heard you can use a 91-94 kdx250 6 speed tranny in the cases with the use of collars on the shafts is this kind of tranny good to use on a mx track as well as the woods? Thanks for any and all input guys!

[zz3gmc]

91-94 KDX250 is a 5 speed. The 200/220 is a 6 speed. I believe the older air cooled KDX250s were 6 speed. There is a whole thread on the KDX trans conversion on Thumper Talk in the Kawasaki 2 stroke forum. A guy that goes by the name No1Clyde is the guy that has done it. The 200/220 trand wont fit the 250.

[funke93]

Yes, I read No1clyde's post on the tran's swap very detailed I guess I just missed the part where the kdx250 tran's is only a 5 speed, and just assumed since it was a kdx that it had 6 speeds? Why do people do this swap then more woods friendly? Why don't they just take the shorter first gear from the 94-96? Kx250 don't quote me on those years haha

[motopunk]

Yes, I read No1clyde's post on the tran's swap very detailed I guess I just missed the part where the kdx250 tran's is only a 5 speed, and just assumed since it was a kdx that it had 6 speeds? Why do people do this swap then more woods friendly? Why don't they just take the shorter first gear from the 94-96? Kx250 don't quote me on those years haha

funke93  the kdx200/220 motors are based on the kx125 motors . directly interchangeability of the complete trannys to the 250 engines are not impossible but why do this? kdx250 trannys would fit better to the kx250 . here you can find some more infos that you looking for.  www.cmsnl.com

[don46]

I didn't mean to imply that the KYB stuff was terrible, because it can be made really good also. you can find 250f Showa components  pretty cheap on ebay the 08 09 and 10  are really good in 11 I believe they went to the sff, I guess for a 250 that would work fine as well, don't hink I'd use it on a 500 though. Having ridden both the 250f and the 450f, i would go with the 250f chassis because it feels smaller and more nimble, even though you would have mmore room, why. refresh my memory is the headstay in the front or back on your motor, I'm remembering the front whic should eliminate any plug to tank issues, heck Service HOnda is using the 250f chassis for their 500's so there is plenty of room.

[funke93]

Motopunk punk thanks for the site! Never even heard or it didn't really get much time to play with it but it looks like I can cross reference part # with different model bikes? Why wouldn't you want a 6 speed tranny in a kx250?! (; and yes don my motor is supposed to have the head stay in the front I think in 03 they switched it (I don't have the head or cylinder yet), but aren't the heads from the 99-02 motor interchangeable with the 03+ motor? Also for frames they all are aluminum from 07 to present is there any particular year that stands out ( kinda like the 08 crf250 frame where they got the hpsd as an example)

[motopunk]

Motopunk punk thanks for the site! Never even heard or it didn't really get much time to play with it but it looks like I can cross reference part # with different model bikes? Why wouldn't you want a 6 speed tranny in a kx250?! (; and yes don my motor is supposed to have the head stay in the front I think in 03 they switched it (I don't have the head or cylinder yet), but aren't the heads from the 99-02 motor interchangeable with the 03+ motor? Also for frames they all are aluminum from 07 to present is there any particular year that stands out ( kinda like the 08 crf250 frame where they got the hpsd as an example)

yes same numbers are the same unchanged part in every bike... 

why i dont want a 6 speed-tranny in a kx? i personally dont need it for my riding ... what i tried to say was the possible easier interchangeability.. 

kx 250 heads are interchangeable from 93-2004 ... 93 is the paralell cooling system with 2 small tubes on the top, that will not fit to your needs...  94-2002 is with front mounting .. 2003-04 with backmounts

[funke93]

Ok so here's the combo I think I'm going to use I have 99-02 cases with the 03 head, 94 cylinder with 94 pv, cdi and stator, and a 94-98 kx250 1st 2nd followed but an 02 3rd 4th and 5th. This is mostly going to be a trail machine with a touch of track riding here and there. Tell me if you guys would do anything different 9oz FWW?

[sandblaster]

I don't see any issues except I'm not sure about your gear choices as I have never tried it.
Motopunk or a few others could probably tell you.
9oz FWW would be great for the trails but it would depend on the track...

[funke93]

Gear choice is what no1cylde is running on his 250 over on TT, it seems like he has a good idea on the internals of these bikes. If my reading was correct I would need to use a 94-98 output shaft as well. Thanks for the info guys and sorry for the late response!