1993 KDX 250 restoration/build thread

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1993 KDX 250 restoration/build thread

Postby romanm » 11:56 am Mar 26 2012

YEs I did have another thread about this, but I want to start over to have less clutter........Im restoring my 93 KDX 250.

Here she is in all her shining glory. Stock other than a full FMF woods exausht.





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Here is me throwing a nice roost in my cousins backyard. This was also one of the last times it would be ridden. It was very tempermental to start. The compression was on the low side at 130 psi, and I had suspect leaking crank seals due to tranny fluid that would need refilling every now and then, and crazy spooge.





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After this one evening, I brought the bike back to the gf's, went to strart it and it sputtered and died. I coulndt get it to fire. I decided to do the right thing and rebuild it. So i brought it into the garage and took the motor out, and took the top-end off.



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Cylinder walls. Not the best of shape, but Ive seen worse. Maybe I could get away with a quick scuff and toss in a new piston and a fresh set of rings.


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Lots of blow-by on the rings. Im assuming stock piston/rings. Bike has about 4000km on it.




So the motor. Whats going on with it you might ask?

Well, the kdx is based of a 90-91 KX 250. This bike has a smaller carb, a 5 speed wide ratio tranny, heavy flywheel, lighting coil, and a cylinder ported for lots of low-end torque and good midrange power.

Now, I love the feel of this motor, but getting the cylinder re-coated is about 300 bucks. This really is the best thing to do here.....but I bought a parts bike. a 91-kx250. It has a jug that is sleeved and ready to accept a new bore and a new piston. Rebore and hone will cost me 90 bucks. This will be most likly the route I take, as Im looking to do this on the cheap. Enough about the motor.....more on it later.




So the frame. Like I said, I bought a 91 KX 250 parts bike. Basically these were the usable parts.

-Forks. rebound and damping adjustable with stiffer stock springs. The KDX forks are garbage. not adjustability....really soft springs

-Wheels. Both look to be in decent shape...no bends. They both need new bearings though. Tons of slop.

-Plastics/gas tank. Useless to me though. I will just use the tail as that is all that fits. Will try to sell the others.

-Exaust. Pro-circuit. Little bit dented up. Cleaned up nice. It will be for sale as I want to keep my woods pipe....its in better condition and I also want to keep asmuch low-end as possible.

- Cylinder jug that has been sleeved. Next size is the final size at 68.5. Will be a 265cc motor with that piston.

- Crank. Fought a battle with a piston and looks like it won. Little scarred up but its still tight.....no up-down play and less axial play then my crank.



So. My garage two weeks ago. Getting shit ready to be sand blasted. Stripped all the old parts off the donar bike, and the project bike

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Trying to stay organized



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Old KX 250 frame.....put it on the curb. This thing was ridden hard and put away wet. Mounts were busted.....aluminum re-welded...races were rusted....just a mess. And it only weighed 5 lbs less than my KDX frame. I decided to cut my losses short here.

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So everythign is apart and ready to get blasted. Its so nice having access to a sand blaster

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Loaded up in the back of the M3



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5 hours later..........



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First coat of Tremclad oil based primer......


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Second Coat


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First coat of paint. Tremclad Semi-gloss black. They were out of gloss black. I will be doing two coats of this stuff, and then one coat of clear ontop of it. This poject is a budget rebuild, with minimal cut corners.

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So with the warm weather, I got the first coat of paint on. 1 can was used. I also got around to cleaning up the bearing on the suspesnion linakage. The KX has different dimension on the linkage. Im sure its better, but with all the bearings being seized in it....Im not wasting my time with it. So i cleaned up the KDX one. The bearing will still good. i also gave it a light sanding with 400, 600, then 800 and some mother polish. Air dried the bearings...sprayed brake clean in...blasted with air. Once I was happy with there beign no water being in there, I packed it with wheel bearing grease and re-assembled. It works nice and smooth now.


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And thats where the project sits now. I have TUSK tools comming in the mail so I can work on my engine. Thats the next thing.

I will also be ordering new swingarm bearings (they were done)....polishing the rear swingarm and greasing a few more bearings on it. I will toss in the old shock. I will have spare KX shock rebuilt later this year, and ill swap it in then. At the same time I will repack the linkage bearings again and install zerk fittings.

The next two big hurtles are finsihing paint (problem is its cold again and I want the paint to dry properly), and the rebuild of the motor. (truing the crank, new crank bearings, all new seals, bore/hones, freash piston.....and ofcourse a coat of paint)

Im hoping to be riding again in two months
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Postby Fletch » 07:31 pm Mar 26 2012

Nice :pop:
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89 kdx 200 with 99 rm125 forks
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Postby sped66 » 07:08 pm Mar 27 2012

Always fun to watch threads like this. :cool:
In the stable: '00 KDX220R, '02 XR250R
Gone but not forgotten: '87 XR200R, '80 XR80
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Postby romanm » 10:54 am Mar 28 2012

Question.

Im about to order some crank bearings. Can I get them locally, and get some good ones like from timkin or FAG?

I see on ebay they have them, but im not sure which ones are good. I dont want some cheap chinese shit. I hate chinq bearings.

Also, from what you can see with my jug....do you think I can get away with sanding it with 400/600 and reusing it? there is only one gouge that can be felt with my finger nail. Also two of the ports have some weird wear on them were the coating is gone as can be seen in the photos, but im not sure if thats going to have that much of an effect. I cant see it causing a ring to snag, can you?
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Postby romanm » 07:25 pm Mar 29 2012

So, I did some cleaning today on the stock jug. Used a combination of a scotch-bright pad and some 600 grit and lots of hot soapy water.....followed by a liberal dose of wd-40.

Im really considering using this jug now as Im not sure its in all that bad of shape. Sure two of the ports have some odd wear on the top and bottom of them....and I have one cut in the wall I can feel with my finger but other than that its good. Id rather get the cylinder replated maybe on the next rebuild (40ish hours).

Anyways, with further ado, please let me know what you think.

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Postby Fletch » 08:17 pm Mar 29 2012

Looks to me like the plating is worn off in a few places. What piston were you going to put in? Do you have access to a bore gauge to measure accurate wear? If not I'd run it but with a new piston ONLY if you're super tight on cash, otherwise, I'd get it plated now and honed to a wiseco and then forget about it!
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Postby romanm » 08:57 pm Mar 29 2012

I only see two ports where the piston is worn away. Keep in mind the bore is covered in oil so maybe something you see is really just alot of oil? Please point out to me where you think it is worn out so I can inspect it better.

Piston would be a new one. I was thinking about using a Pro-x. If it will work fine for another 40 hours Id rather just go this route and do a replate then,

The other option is using the steel sleeved kx jug I have and boring/honing it to the next size. How long will that last though? Im thinking same as this top-end would since it wont be as hard as the coating. But I might be able to sell it to recoup some money so Id be more inclined to do that instead.
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Postby romanm » 11:11 am Apr 04 2012

Update.

Doing a big purchase here boys. Need alot of stuff replaced. Prices in Canada are pretty high, so im ordering online and picking this up from the states and driving back. Its going to save me a couple hundred.

So, if you feel like im missing somethign please let me know. Im doing one big purchase....any other odds and ends I miss will have to be bought locally.

ENGINE
-Full gasket/seal kit
-Stock size pro-x piston (yes im reusing my jug. Itll have to do for now)
-Crank bearings
-Clutch cable
-Ait Filter
-Dual stage Reeds

DRIVELINE
- F&R sprockets
-Chain
-F&R wheel bearings
-Chain rollers
-Chain guide

CHASSIS
-Swingarm bearings
-Brake pads
-Fork rebuild kit
-Grips
-Brake Lever
-Hand Guards
-Skid plate
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Postby chadr » 12:16 pm Apr 04 2012

I was looking at a pro-x piston on ebay and noticed it didn't include the small end rod bearing. Do most people replace that with the piston, or just reuse the old one?
1989 KDX 200
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Postby Fletch » 12:25 pm Apr 04 2012

>|<>QBB<
chadr wrote:I was looking at a pro-x piston on ebay and noticed it didn't include the small end rod bearing. Do most people replace that with the piston, or just reuse the old one?

Replace
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1993 KDX 250 restoration/build thread

Postby romanm » 05:57 pm Apr 23 2012

Hey everyone.
Im just wondering what piston clearance I need to run. Its the stock cylinder I will be using...and it measured out to be 67.41668mm. I also measured at the top part of the bore...where there are no ports where the gas gets compressed....is this correct?
So now I need to figure out what size pro-x piston to get.



Here are a few picks of how the project is comming

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Still gotta order all my parts....for sure happening this week...once I know what sized piston to get ahah.


Thank you
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1993 KDX 250 restoration/build thread

Postby Thack » 08:36 pm May 14 2012

Nice start. Cant wait to see it finished.
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1993 KDX 250 restoration/build thread

Postby B-mo » 09:10 pm Jul 24 2012

Is that 250 Gastank still for sale from your parts bike?
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Re: 1993 KDX 250 restoration/build thread

Postby KDXrider1989 » 02:19 am Jul 25 2012

nice polished swing arm, I plan on doing that on my 200. how'd you get it so shiny?
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