2003 KX 250 SF Conversion

[umberto]

I've been sitting on a 1989 K5 engine and goodies that I bought off of eBay for a while now. I'm about ready to start the conversion into a 2007 KX 250 that I have owned for several years.  I'm taking a welding class at the local technical school, and needed a project to practice on, so off we go.  The class starts in June, so I am beginning the process of getting everything swapped and the mounts and pipe ready for welding.  I have already procured the correct drill bit, and the used CR 500 pipe is on its way.





I will be selling the 07 250 motor if anyone is interested (I will list in the for sale section when I get it ready).  I am putting a fresh top end in the motor with a Wiseco forged piston, Wiseco rings, bearing, wrist pin, and clips.  I am also going to clean and inspect the power valve, and do a leak down test.  I will be selling the motor with the FMF Gnarly pipe, carb, and electronics.  It would be a perfect engine for an AF swap.  I'll even ship it for free.  I should have some pics and video of the rebuilt engine by next week.

[kawboy]

What brand side stand is that on the 250 ? I really like the way it mounts. That 500 engine looks like an '88 , but I could be mistaken.

[umberto]

It is an 88.  I've had it so long, I forgot the year.   . The side stand is made by Trail Tech. It says it only fits up to a 2005, but it has been on both my 07 and 04. They run about $120, and I got mine from Rocky Mountain. If you buy one, got to Trail Tech's website and buy a replacement foot for $5. I took about a half to 3/4 of an inch off mine and it works much better.  To cut it, you will have to cut the foot off with the aluminum tube.  The feet are impossible to remove. Or you can stack the spacers, but that makes the mount stick out a bit more at the bottom.

[kawboy]

Thanks. My '05 needs one of those.

[umberto]

I got the top end rebuilt on the 250 today with a Wiesco forged piston, bearings, and cometic gaskets. I've rebuilt tons of two strokes in my day, but I still get such a rush from taking one apart, putting it back together, and hearing it fire right up. This thing sounds stout, I can't wait to ride it tomorrow. I'll break it in, and probably get it on eBay next week. If someone on here would like it, I will make you a deal for less than I'm selling it on eBay. The package will include the engine, carb, electronics, and FMF Gnarly pipe.  This was my personal bike, and was never raced or abused. I put about 40 hours on a rebuild I did when I got it.  When I put the new piston in today the bottom bearings felt excellent, and the seals were in great shape.

[umberto]

So I got the 07 KX motor all broken in and ready to go, but I had an epiphany as I was riding the bike.  I don't like the 07 as much as I like the earlier 03-05 KXs.  I feel like a K5 motor is a rare gem and must be placed in the best frame it can be, so I am thinking about selling the 07 in one piece and buying an 03-05.  I'll sell the 250 motor and stuff the 500 in it. 

I found this bike for $2,000 about 200 miles away.  It has Pro Circuit exhaust, Piper Suspension set up for 150 lb rider, and has a fresh motor (according to the seller, Umberto's compression tester will be the judge of that).  The wheels do not come with the bike (which I was going to add my own wheels anyway).



I also found this 2004 that is about 100 miles away.  The bike is all stock, and the motor has not been messed with.  Dude started out at $2,300 and is now down to $2,200.  I don't think he is going to wiggle much more than that.  I told him I was considering the 2005, and he only budged $100.



I figure I can sell my 07 for $2,250-$2,500 and sell the KX motor for $1,500 or more (the 05 motor with an aftermarket pipe should bring more) so the money makes sense.  My question is this:  Is the 2004 better than the 2005, and if so is it worth that much more (especially considering the aftermarket parts on the 05)?

[KevinTwoStk]

I think the '05 is very similar to the '07...so if you're looking for a better-handling bike than your '07 I'd stick with '03 or '04.

[KXDINO]

the 05 frame is the same as a 07 , if you want these models to handle you have to change head angle , see kawi had the frame set at 27 degrees on 03 and 04 , than some bird brain decided to steepen it to 26 degrees for the 05 model and kept the same frame until its demise, we modify the frame so the angle is 26.5 , bingo ,no more front washing out threw the corner.longer pull rods help a bit to , but i prefer to fix the frame and be done with it.

[umberto]

I decided to go with the 04 and even negotiated a better deal, but now the guy isn't texting me back.  Or as I like to call it, The International Craigslist Passive Aggressive Signal for I Sold the Bike or I Don't Want to Honor the Deal I Agreed To (I.C.P.A.S.F.I.S.T.B.O.I.D.W.T.H.T.D.I.A).   

I found this bike, which seems to be a better deal, but he won't text me back either.  It's only been on 3 days, so I'm hoping he works nights, or is at work and can't text back.

[umberto]

I found another 2004 and he is not texting me back either.  It's been on Craigslist for just 4 days.  I am beginning to think there is a conspiracy against me acquiring another 2004.  Maybe having two of them is too much of a good thing?   

[KevinTwoStk]

Shoot! There's another '04 with your name on it...somewhere.

[umberto]

So both guys texted me back within 15 minutes.  And my wife says complaining never gets you anywhere.    The owner of the first bike may trade for a 4 stroke, but if not it's mine.  The second bike I found is a 2003, but is mechanically pretty sound.  It has a new motor with 10 or 11 hours, pipe, silencer, and Magura hydraulic clutch which intrigues me.  Of course it's 4 hours away instead of two. Here is the 03:

[umberto]

So I picked up the 03 today.  The motor is really crisp, and there was nothing glaring (that I wasn't going to replace anyway) wrong with the bike.  The Magura clutch is awesome.  Has anyone tried one with a K5?



Here's the Magura clutch cylinder:

[KevinTwoStk]

Good deal! That's a nice looking '03.

I can't speak for the Magura hydraulic conversion on a KX500, but I do have one on my '00 KX125. With all the clutch abusing required to ride a 125, I think it's a pretty good barometer for the Magura system.

I've had zero troubles with the slave cylinder, but I've had to replace the seals a few times on the master cylinder. As for performance, it's everything it's supposed to be: self-adjusting, easier lever pull.

Motocross Action featured a KTM/KX500 that used a Magura hydraulic conversion. The 250SX uses a Magura master cylinder, so they just added the KX500-spec Magura slave cylinder. I assume it worked well.

[umberto]

Does anyone know if the swingarm needs to be trimmed for an 88 K5 in my 03 frame?  If it does need to be trimmed, do you need to trim equal amounts off each side, or do you need to offset it to one side or the other?  Thank you for the help, I don't want to make a costly mistake right out of the gate.