2003 KTM 125SX: $400 Craigslist Special

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11/20/2017 8:21 AM

So I picked up this bike for 400 bucks, missing some bits and low compression. Been heavily considering parting it out as opposed to rebuilding it as some guys recommended me on an orange forum, the argument being "if you part this out and get some more money together you can get something pretty nice." I've been looking.. and it seems the 3k-4k bikes out there are STILL going to need some work, and I'm not quite ready to drop so much down on the hobby, with my skill level the bike probably won't make a difference.

So my goal here is to (hopefully) keep everything under 2 grand including the cost of the bike, and have a nice, fresh, fully rebuilt bike. Won't be tricking it out with all the hard parts, but hopefully I can get it sorted and have it be a nice bike for the next year or 2 until I get a bit better riding and figure out what I really want before dropping a lot on a bike.

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As you guys can see..Missing a few bits. Now into the engine! So when I got the bike, did a quick compression test and was low, holding 90 consistently. I got home and pulled the head off and..Brand new piston, never fired. cylinder completely dry, no oil. Which could contribute to the low PSI, but I noticed the power valve actuator arm was rusty, which had me a bit concerned. So I decided to split the cases and figure out what's what before I put the time and effort into sorting the top end. There was some rust on an aftermarket crank, and a circlip dropped in the cases. So at this point I'm already budgeting for a crank rebuild.



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Opening up the right side of the engine we find...Water. A good amount of water. And a few pieces of hair! The inner clutch basket has one of the posts snapped off, it will have to be replaced. What's curious about this all is that everything looks brand new, the bearings, there is assembly lube on some of the components, etc. It'll all have to get replaced of course because it was sitting in water, but I'm just curious as to what the hell happened. Someone was in the process of rebuilding but never finished? and left it with the head off and it got moisture? internal leak? Rage quit the project when they were putting it all together and dropped a circlip inside? Next update I should have the tools to split the case and see what else is going on here.

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11/20/2017 9:12 AM

Man id be so pissed if i found all that in a bike i just got. Guess you cant expect anything less for $400. The guy clearly knew he done fucked up on the motor assembly

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

11/20/2017 9:15 AM

It's not too bad! Well, let me rephrase that lol. It's not unexpected.

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11/20/2017 9:24 AM

I've got a bunch of parts that will fit your bike that you may be interested in. I've got cylinder heads, cranks that are in good shape, vforce reed cages, etc. Willing to let them go cheap as I have no use for them and would like to help out another member. Send me an email at samcam28@gmail.com If interested.

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11/20/2017 9:30 AM

That would be AWESOME Sam, I'll get in touch with you right now.

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11/20/2017 10:05 AM

At least you will have a decent bike when it's done, I had one of these and I remember it being a rocket.

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I no longer regret my username.


11/20/2017 11:01 AM

I must say 400$ for that is a pretty great deal, for me at least here in ny. If I could find a bike like that for 400$ near me Id 110% grab it. deff a fun project. Looking forward to seeing the end result!

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dirtbike kidd

11/20/2017 1:07 PM

Sam here helped me out with all kinds of bits, hopefully getting a care package here at the end of the week!

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11/20/2017 2:09 PM

I remember these bikes when they were new and they were lightning fast! There's also lots and lots of Ohlins and Trax PDS shocks knocking about, so you could even find one of those and work out a way of making it fit it your budget allows. Enjoy the build!

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11/20/2017 2:42 PM

We all like to see a good rescue build....bring her back!

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11/20/2017 3:14 PM

Goatsby wrote:

It's not too bad! Well, let me rephrase that lol. It's not unexpected.

Not to rain on the parade but looking at the pics, it seems like the intake port opposite from the exhaust is cracked on the top edge of it...better look closely at that

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Many thanks to everyone helping me out this GNCC season: SRT Offroad, Acerbis, FCR Suspension, O'Neal Racing, Evans Waterless Coolants, Rekluse, Twin Air, Braking Brakes, Carbsport

Profile image credit Ken Hill Photography

11/20/2017 3:25 PM

So looking at it I think you're right, that puts a bit of a damper on things. Here are some more pics, looks like a chunk is taken from the wall almost. Now that being said, should I spring for a 200 conversion if I'm going to have to replace this either way? I found a guy who has a 2016 200 cylinder with the complete power valve and he wants 400 shipped. I'd still need the crank and head.

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11/20/2017 3:36 PM

Good luck, that seems solid for $400.

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11/21/2017 1:51 AM

Cool bike! You could build a Langston replica out of it.

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11/23/2017 8:13 AM

Sounds like a sweet deal!!

Man, it's weird what some people do with their bikes, isn't it? Like, did the bro leave the motor out in
in the rain disassembled or something? Tweakers!

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11/23/2017 8:52 AM

JMX82, that's what I was thinking, that or either update the plastics style with a new airbox/subframe/tank. I'll have to be replacing due to someone cutting holes in them/ old age. Chip, that seems like exactly what happened lol. Someone left the bike outside with no head on.

Parts coming in:

Almost new 200 cylinder and head, 2016.
Brand new hot rods bottom end kit.
New Wiseco 200 piston kit.
A box of parts from a fellow VitalMX member.

Quickly running out of budget, but we'll make do!

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11/23/2017 9:23 AM

If your going 200 route you HAVE to build it, loved mine

Looking forward to see how this goes

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Now a member of the Orange brigade

11/23/2017 9:30 AM

What kind of set up did you run on yours?

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11/23/2017 10:36 AM

It seems that you already have radiator shrouds, front fender and front number plate from 2006 model. You could use subframe, airbox, seat and rear fender from a 2004-2006 model to complete the look. I think it's direct bolt on modification and was quite popular back In the day.

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11/23/2017 9:50 PM

You're going to make it a 200??!!! Hell, yeah!!! It will RULE!
I have a 200EXC and it is friggin AWESOME. Perfect motor. You will love it!!

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11/23/2017 11:03 PM

If you choose to go with newer style plastics you could build a Tyla Rattray replica.

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11/24/2017 12:24 PM

I think this will be useful when you start rebuilding the engine Engine manual

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11/24/2017 3:08 PM

That looks sweet JMX82. And thanks for the manual, I found the same one online, should definitely come in handy!

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11/25/2017 12:01 PM

I got a package in, it looks nice. Just waiting on the new bottom end kit. Photo

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11/27/2017 9:27 AM

Waiting for more parts still, completely forgot about the transmission bearings as well, so those will get ordered today. Did this in the meantime! Waiting for it to cure a few days, and then going to wrap the high wear areas in a clear protective vinyl.

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11/28/2017 1:43 AM

Hold on to that cylinder. It might be repairible. I had one that looked worse than that. Sent it to Ken O Konner Racing. He TIG welded it, machined it down then replated it. Looked brand new when I got it back.

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11/28/2017 7:00 AM

I've gone up to a 200 bore so it won't be much use unfortunately. It's very clean though, same with the power valve. I'll probably have them up on ebay today.

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12/26/2017 9:12 AM

A long awaited update! I got busy and couldn't put much work into the bike for a while but I'm back at it now.

New bottom end bits arrived, and the cases are sealed.

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I was ready to put the whole engine back together today, and was quite surprised the previous owner's attempt at rebuilding the engine didn't result in any lost parts when...

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The Driver Hub of the kickstarter is missing! I posted on a KTM specific board to see if anyone has that piece laying around who could give me some measurements. I'd like to make one today out of aluminum just to bypass waiting 2 weeks from the OEM supplier for a 3 dollar part to finish the engine.

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1/9/2018 7:39 AM

Goatsby wrote:

Waiting for more parts still, completely forgot about the transmission bearings as well, so those will get ordered today. Did this in the meantime! Waiting for it to cure a few days, and then going to wrap the high wear areas in a clear protective vinyl.

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What paint did you use? i have the same model bike im planning to frame up also

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Instagram @factoryfarley25

1/31/2018 7:36 PM

Sorry I just saw your post! I rattle canned it with krylon and primer. It looks good at 10 feet but there is orange peel. If I were to do it again I'd use an HLVP and sand blast it. If I wasn't a cheap bastard and would do it again I'd have it powdercoated. But it'll do.

Long time no update guys, was in the UK for a month staying with my girlfriend. Got back a week ago and starting to work on the bike again. This is the current state of things. A quick question on that note - is the reed cage gasket supposed to go between the case and the reed cage, or the reed cage and the carb boot? The gasket doesn't fit on the OEM cage case side, but does on an older V-force reed set I have. Tomorrow I'll hang the engine in the frame and do a compression test.

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