KDX250 info

Kawasaki KDX 250
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argclh6670
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KDX250 info

Post by argclh6670 » 12:14 am Jan 03 2013

#1
Figured some good info on the bikes would be a great sticky.

The KDX250 is a lot like the WR250 and RMX250 of the years. They are an enduro model MX bike from the factory. They suffer from poor jetting, engine performance and suspension. The factory added a XR style rear change adjuster, kick stand, larger tank, Wide Ratio tranny and lighting stator to the KX motor make up the mods to make it a KDX model.

To get the bike into peak performance, you will have to start with the motor, then jetting, then suspension.

Where to start your modifications:

]freebies:
1) Remove the airbox snorkle from the lid and cut the lid open to maximize air volume intake.
2) put the needle in the second notch from the top (carb will still be jetted to rich)
3) set the sag on the rear suspension

now you will find that the bike still has carb issues, performance issues and suspension issues. So you will be putting some money into the bike to make it into what I can become.

]money mods:
1) KX250 thin headgasketfrom 1988 (.26 vs .46 in thickness)
2) Rejet the carb -- 38 slow, 158 main, #6 slide, R1367 needle 3rd clip. This will bring the bike closer to the KX spec.
** I ran 50:1 amsoil, so jet according to altitude and mixture.
3) aftermarket pipe (anything is better than stock)
4) aftermarket silencer/SA
5) aftermarket reeds (Vforce recommended)
6) NGK Iridium IX plug (BR9EIX)
7) install stiffer fork springs (at least .38s from a KLX300) with new 2.5 or 5w oil
8) port the cylinder[/size]
9) have the cylinder head squish redone[/size]

That will get the bike's motor and jetting where it should be. It will be a different bike all together with those mods. Be sure that you inspect the clearances and replace internal parts as needed since these are old and used bikes. Also inspect the power valves, clean them and be sure they are timed properly.

The suspension will still be hurting. I found a set of 43mm forks off a early 90s KX250 and rebuilt them, then installed them on the bike with the KX front wheel. You will lose the odometer but with aftermarket units like the trailtech setups, you can easily upgrade there. The KX front suspension is a must do upgrade for anything faster than 1st gear on these bikes! For the rear, you can simply revalve and respring the stock shock.



Where parts come from:

Keep in mind that the 91-94 KDX250 was built off the 88-91 KX250 bike mainly. There are some differences between the bikes, but if you get stuck trying to find a part, be sure to cross reference those year bikes first. There are also a lot of bearing and clutch parts used of the KX500s of the same years.


-Brake Pads: KX125/250/500 89-93. pads and rotors are the same as the 89-02 KX125/250/500 for the 91-94 kdx250. So you can get the ceramic pads and wave rotors. Brake lines seem to be different though same with the Master cylinders. You can run the KX front and rear SS aftermarket brake lines without issue. A great upgrade is a 02+ CR/CRF honda front master cylinder with lever. The 07+ have the linkage for even better performance.

-Steering head stem bearings list the same for the 80-91 KX250 and KLX250 94-96

-For the Fork seals, the 88/91-95 KX250, KLX250/300 fork seals list the same as the KDX250 units (43mm units). The stock is a 43mm ID x 55mm OD x 9.5mm height. you can run the 10.5/11mm tall seals for beatter sealing.
-Fork gaurds is the same as the KLX250/300. You can run the 90-93 KX units also, but they offer no side protection to the forks

-Rear brake holder/bracket -- same as 89-94 KDX200. Use this for the rear shark fins & scotts gaurd

-Front Forks: Kayaba. .35 kg for 92-94, .34kg for 91. 43mm inverted. (similar forks as the KLX 250/300 bikes). compression only adjustment and very poor forks for anything but slow speed work.

-Rear shock: 4.8kg for 92-94, 5.0kg for the 91. Spring same for 88-02 KX and 89-94 kdx200. Eibach 996 series

-Sprockets seem to be a KX/KDX thing. No differences there.

-aftermarket Chain rollers = Small

-Chain Guides: 88-96 KX 250/500, KDX200

-Reeds are the same as the KX500 units in FMF. Boysen same as 89-96 KX250. Mototassinari use the KX500 Vforce kit.

-Lower shock bearing/seals is the same a 88-01 KX500

-Unitrak bearings are the same as a 88-01 KX500

-Rear swing arm slider is the same as the 94 kdx200 , 89-01 KX500

-Rear mudflap is the same as the kx250 (90-91)

-Looks like the seats are a bit different, but a cover would most likely fit both From a 91-94 250 or 89-01 KX500.

-Clutch: 89-01 KX500, 88-91 KX250

-Clutch cable 90-91 KX250

- Throttle Cable : 88-91 KX250, 88-02 KX500

-Top End gasket, same for 88-91 KX250 (stock thin head gasket .26")

-Piston Needle Bearing 74-02

-Connecting Rod 78-02 KX250

-Piston & rings KX250 90-91

-rear bearings wheel bearings: Timken 104 series bearings. You can pick them up at any autoparts store.

1986-2002 KX125/KX 125/KX250/KX 250 and KX500/KX 500, 1989-2002 KDX200/KDX 200/KDX220/KDX 220; 1991-94 KDX250/KDX 250; 1993-96 KLX650A/KLX650R/KLX650/KLX 650; plus the 1983-84 KL250C/KLR

-Front bearings:

Timken 202 series bearings. You can pick them up at any autoparts store.

KAWASAKI: 1983-83 KX125/KX 125; 1968-70 F3 175; 1983-96 KDX200/KDX 200 1969-70 F4 250; 1971-72 F8 250; 1973-75 F11 250;1982-84 and 1991-94 KDX250/KDX 250; 1994-95 KLX250D/KLX250R/KLX250/KLX 250; 1970-75 F5/F9 350; 1993 KLX650A/KLX650R/KLX650/KLX 650; 1993-96 KLX650C.


For the plastic, you can easily run KX front fenders and number plates. The side plates and radiator scoops are KDX250 specific. I used a 1990 KX250 rear fender for a MX look with minor trimming.
Last edited by argclh6670 on 05:00 pm Mar 09 2013, edited 1 time in total.

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Julien D
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Re: KDX250 info

Post by Julien D » 03:25 pm Feb 15 2013

Stickied, thanks for writing this up!
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zz3gmc
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KDX250 info

Post by zz3gmc » 04:06 pm Feb 23 2013

The KDX250 chassis wasnt based off of a KX like the WRs and RMXs were. The frame was very differant from any of the KXs of the time. I raced a 90 KX and you couldnt swap plastics, tanks easily like you could with the WRs and RMXs with there MX counterparts (YZs and RMs) I remember seeing pics of Team Green KDXs where they tryed to adapt KX tanks and seats to get the better ergos of the KXs with out much success. The engines definately had KX lineage.

argclh6670
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Re: KDX250 info

Post by argclh6670 » 11:01 pm Feb 24 2013

You are right, the chassis NO. Engine yes (wide ratio trans and heavier fw) and that is what I was referring to.. if the chassis was. Like the kx then the bike would have been much more popular and had a much longer production life.

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KDX250 info

Post by zz3gmc » 12:41 am Feb 25 2013

I wanted one bad when they came out! Alot of racers bought them and did fairly well with them. My friend bought a new 92 and I tryed it out. I loved the motor, his was uncorked, but couldnt come to terms with the handling in the tight woods. Especially coming off of a KX250. I ended up jumping over to the 200 class and bought a 92 KDX200. The 200 just out handled the 250 in the tight stuff but was down on power compared to the 250. I do have a soft spot for the 250 and wouldnt mind picking one up someday.

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Re: KDX250 info

Post by jgas » 05:22 am Oct 12 2013

Where I look for info on older mdx 250s? I have an 81 and am buying a 79 for vintage racing in AHRMA and also for trail riding. Thanks.

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Re: KDX250 info

Post by jgas » 06:03 am Oct 12 2013

Duh, never mind! I just found the air cooled section.

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Re: KDX250 info

Post by Ron-e » 07:19 pm Mar 10 2014

Do you know if the 94 KX 500 rear wheel will fit the 91-94 KDX 250? I know its different tire size but will the whole rear wheel work, spacing, brakes, ect.

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KDX250 info

Post by dingerjunkie » 09:24 am Nov 24 2014

Just wanted to consolidate information to this thread with a question related to parts compatibility.

Radiator options...one thread stated that the 88-89 KX250 radiators are a direct bolt-on. Has anyone here on the board done this swap to verify before I drop coin on a new set from Myler's? They make a really nice set for the '89 KX250, but I'd hate to waste the money and find out that they are not actually a bolt-on swap for the 91-94 KDX.

Who has replaced successfully with what for radiators on the KDX250D series?

UPDATE: did some digging at BikeBandit. Left-side radiators between '98-KX250 and KDX250D share part numbers. Right side does not. Is anyone familiar with what will fit the right (pipe) side?
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