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I have a 1998 kx250 and I absolutely love the motor on it but the frame, suspension and fenders are dated and it handles like a tank, I want to try and convert it into a newer style kx250 with my 1998 motor. I have been looking for a while and i think that i would be able to make it into a 1999-2002. has anyone ever tried this or knows any info that could help me out with this project?

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You should be able to swap the '98 motor into a 99-02 frame without any problems. I'm pretty sure that the motor is externally identical.

I've never ridden a '98 so I'm not sure how much better the L series chassis and suspension is.

There are people on here who can answer just about anyting about those bikes though. I'm sure they will chime in soon.

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It is a bolt in on the 99-02, even your 98's pipe fits. It will fit the 03-04 also if you use the head off the 03-04 since they moved the head stay to the rear.

Ed

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Total waste of money and time.

If you want to upgrade it.....fit your motor into a late model aluminum frame.

That would be great, unless like me you prefer the "feel" of a steel frame.

Like Ed already said, it is a direct swap into a later KX250 chassis.

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No chokey I like the feel of my 94 the little bit I rode it. I was just refering to spending time and money swapping a 98 to a 99-02 seems kinda fruitless for the gains.

I however did like the handling of my aluminum frame CRs alot. The TC showas were also nice.

To the original poster maybe send your suspension to a good tuner and see if that makes the bike better.

I have not ridden the 2000 model KX bikes so may be I am totally clueless to what seems apparent by just looks. Did they change the geometry alot from 98 to 2002?

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No chokey I like the feel of my 94 the little bit I rode it. I was just refering to spending time and money swapping a 98 to a 99-02 seems kinda fruitless for the gains.

I however did like the handling of my aluminum frame CRs alot. The TC showas were also nice.

To the original poster maybe send your suspension to a good tuner and see if that makes the bike better.

I have not ridden the 2000 model KX bikes so may be I am totally clueless to what seems apparent by just looks. Did they change the geometry alot from 98 to 2002?

The geometry was changed in '99, and again in '03. The '02 and up has much better suspension (48mm forks, longer pull rods), much improved brakes (no more mushy brakes), stainless pegs, and a few other changes that make it a worthwhile upgrade over the '98 chassis with it's horrid forks, stinkbug linkage, slack head angle and mushy brakes.

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The geometry was changed in '99, and again in '03. The '02 and up has much better suspension (48mm forks, longer pull rods), much improved brakes (no more mushy brakes), stainless pegs, and a few other changes that make it a worthwhile upgrade over the '98 chassis with it's horrid forks, stinkbug linkage, slack head angle and mushy brakes.

I stand corrected...but all but the neck angle can be converted with aftermarket/later model parts?

Is the 98 motor that much better than the later models? Is it cheaper to sell the 98 and buy a complete later model bike and add a bigbore? :smirk:

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all the steel frames from 1994-2002 are pretty much the same with minor changes through the years. the suspensions changed. if your after plastic changes, than you need to modify your frame, get the correct subframe as they changed quite a bit. airbox and seat. its alot of work, grinding and welding, and alot of cost investment. if you want to spend the money, convert an aluminum frame like blackwoods suggested or buy a 99-2002 roller and put your motor into it. just my thoughts

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I stand corrected...but all but the neck angle can be converted with aftermarket/later model parts?
Yes, but that route can cost more than just finding a decent rolling chassis and sticking your engine in it.
Is the 98 motor that much better than the later models? Is it cheaper to sell the 98 and buy a complete later model bike and add a bigbore? :smirk:
It depends on your idea of "better". The '98 had explosive low-end and midrange power that no KX250 since has had, but it had essentially no top-end. The low-to-mid power was considered by many (including MXA, who named it BOTY) to be the perfect motocross powerband. It excelled at blasting through berms and clearing obstacles right out of turns. But many riders complained about the abrupt hit and lack of top-end, so Kawasaki spent the next couple of years softening the low-end and trying to move the power up in the rev range. In doing so they lost that magic low-end thrust that made the KX so potent on the track. In '02 they reversed course and tried to get back some of the low-end, but in comparison to the '98 my '02 has better midrange and top-end, but nowhere near the low-end grunt the '98 had.
all the steel frames from 1994-2002 are pretty much the same with minor changes through the years. the suspensions changed. if your after plastic changes, than you need to modify your frame, get the correct subframe as they changed quite a bit. airbox and seat. its alot of work, grinding and welding, and alot of cost investment. if you want to spend the money, convert an aluminum frame like blackwoods suggested or buy a 99-2002 roller and put your motor into it. just my thoughts
The head angle was changed in '99 asnd the tank was shortened to move the rider forward, and the head angle and trail were changed in '03. The '99-02 turns better than the '94-'98, and the '03-'07 turns better still.

The '98 will bolt right in to a later model two-stroke chassis. An aluminum four-stroke chassis takes a lot of fabricating and welding, for engine mounts and to move the front down tube to clear the two-stroke pipe. The two-stroke frame swap is far easier to do, and isn't a waste of money.

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Yes, but that route can cost more than just finding a decent rolling chassis and sticking your engine in it.

It depends on your idea of "better". The '98 had explosive low-end and midrange power that no KX250 since has had, but it had essentially no top-end. The low-to-mid power was considered by many (including MXA, who named it BOTY) to be the perfect motocross powerband. It excelled at blasting through berms and clearing obstacles right out of turns. But many riders complained about the abrupt hit and lack of top-end, so Kawasaki spent the next couple of years softening the low-end and trying to move the power up in the rev range. In doing so they lost that magic low-end thrust that made the KX so potent on the track. In '02 they reversed course and tried to get back some of the low-end, but in comparison to the '98 my '02 has better midrange and top-end, but nowhere near the low-end grunt the '98 had.

The head angle was changed in '99 asnd the tank was shortened to move the rider forward, and the head angle and trail were changed in '03. The '99-02 turns better than the '94-'98, and the '03-'07 turns better still.

The '98 will bolt right in to a later model two-stroke chassis. An aluminum four-stroke chassis takes a lot of fabricating and welding, for engine mounts and to move the front down tube to clear the two-stroke pipe. The two-stroke frame swap is far easier to do, and isn't a waste of money.

come on chokey..its all a waste of money but if you work for yours like I do..its mine to waste before the politicians can...I should have said it a alot of money to spend to get it where you think you want it.....and being a man even when we get where we want it...we then want something different. :smirk:

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come on chokey..its all a waste of money but if you work for yours like I do..its mine to waste before the politicians can...I should have said it a alot of money to spend to get it where you think you want it.....and being a man even when we get where we want it...we then want something different. :smirk:
Well, if you want to look at it that way, this entire sport is nothing but a waste of money, but I still think it's worth it, don't you? :bonk:

But by not being a waste of money, I just meant that the improvement is big enough to be worth the effort if you can get the rolling chassis for a decent price.

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IMO, the K model chassis are just as good as the L model chassis. Although I couldnt get my L model to turn for crap, its all about the setup. Also, Chokey, my 98 did not have musht brakes and the issue with the forks was the progressive springs. Swap those out for some straight rate jobs and youre good.

The 03 and up chassis is totally different. My 94 and 98 felt more nimble than my 2000's.

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thanks guys these are alot of great ideas, if my motor would fit into the 03-07 frame that would be even better than the 99-02 but i thought the year difference was so big that there was no way it would fit.

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05-07 is a whole differant bike from the 03-04. The engine wont bolt into a 05-07 frame without cutting out the front motor mounts and repositioning them to fit the older 92-04 engine. The KX got a completely redesigned engine in 05 from the cases up and aside from certain clutch components, nothing interchanges with your 98. It can be done but it would be easier in a 03-04 frame which your engine should bolt right in with a swap to the 03-04 head. The swingarm pivot might be bigger on the 03-04 so you may have to open up the back of the cases to 17mm, not sure about that though.

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The swingarm pivot is the same from 94-07 KX125/250 and 04/05 KX250F. IMO, you're wasting your time with any "swap". When all is said and done you would have spent enough to just buy a newer bike. However, if you just want a project, you should put that engine into an 03+ 250 (steel frame) chassis or 04/05 KX250F chassis along with a set of twin chamber Showas.

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it is just a project. i have a 2009 crf450 that is my mx race bike. i have had the kx250 for a while as my woods racing bike but the bike is so old that it beats the shit out of me when i ride it hard so i want to invest some time and money into it to make it nice again, the motor on it is nice and i have put a lot of money into it which is why i want to keep it and i also have a full fmf gnarly system with it that i want to still use. i love the showas too, my 2006 kx250f had them on it and they were soooo smooth. i definitely dont want to try a swap to a 250f frame because i know that would be super hard with the exhaust for the two stroke and having to cut out a big chunk of the bottom part of the 250f frame. if you guys think i can get my motor into an 03-04 then thats what im gonna do so i dont need to do any welding

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It fits the 03-04 frame with the use of the 03-04 head for the rear mount. You will probably need to move the pipe mounts on your 98 pipe for it to fit but shouldn't be too bad of a job.

Ed

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glad I came across this thread, some good starting info in here! I have my 98 tore apart right now, and have been thinking of pulling the trigger on a newer roller to stick a freshly rebuilt motor into. Loved that motor when I had it before, but after getting my 02 cr, I don't think I could go back to that 98 KX frame!

I've got a line on a 2002 semi complete roller at the moment. With all the goodies Chokey mentioned, It sounds like a worthwhile investment as pretty much my whole bike was clapped out when I tore it down. Suspension front and rear was blown, wheels missing spokes. frames got some cracks at the top shock mount... (gotta love selling to friends who don't treat em right haha :thumbsdn: )

The geometry was changed in '99, and again in '03. The '02 and up has much better suspension (48mm forks, longer pull rods), much improved brakes (no more mushy brakes), stainless pegs, and a few other changes that make it a worthwhile upgrade over the '98 chassis with it's horrid forks, stinkbug linkage, slack head angle and mushy brakes.

guy says it's only missing the rear wheel and swingarm bolt. If that motor is a direct drop in, and the frame looks decent enough, I'll probably go for it. Good luck in your search, MXracer! I'll post back my findings today and get your guy's opnions.

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