2006 KX250F Rebuild

[Slick_Nick]

I bought this bike in the summer of 2018 for $1800. It ran, but not well. Picked it up with the intention of having a new project. It sat in its roached condition in my garage for two years, until I decided that I wanted to get back into motocross. (I ended up buying this bike's twin, a 2007 model, in the fall of 2021, from the same guy I got this bike from.) It's rebuild it forthcoming.

The 2006 KX250F is, in my opinion, my "dream" motocross bike. When I first saw it released, I loved the black and green look, the smooth aluminum frame, the brown-gold triple clamps and engine covers. It was the first year of the aluminum frame for Kawasaki (their previous foray in 04-05 were the steel framed "kawazukis".)

With all that said, lets get into it. When I looked at the bike, it ran, but it popped, it backfired, it was super lean, but the engine itself had no knocks or anything, so I felt safe to assume that even though I intended to do a full rebuild, I wasn't in for any huge ticket items.

Here is the bike as I picked it up, and got it home for a wash off to see what we're dealing with.








Figured I'd hit it with the inspection camera. Lots of carbon, and looks like an aftermarket piston. The cylinder head is a different shade of weathered aluminum, perhaps it was replaced at one point?

[Slick_Nick]

Two years went by, with the bike sitting in the corner of my shop, collecting dust. Finally, in the spring of 2021, I decided I was sick of looking at it, and wanted to get after the rebuild. Lets start the disassembly, and make our parts list. Be warned, some of the following photos are vomit-inducing.












The bolts were rusty, the axles were seized, but slowly we're getting there!

[Slick_Nick]

Project bikes are always FULL of surprises. I really love (and i mean LOVE) how this bike looks stock, so months before this, I had already ordered a new to me (lightly used) stock seat, since I assumed this one had this gross cover on it. But wait... What's this we see underneath it? Half an hour later, and after pulling what felt like hundreds of staples, I was surprised to find, an almost mint condition stock seat cover still in place! There was a white streak on top, but that easily wiped off later on! What a score!






This exhaust is a full Pro Circuit Ti-4 Titanium system. Brand new, this exhaust was close to what I paid for the whole bike! More on refurbishing this exhaust later, don't worry, but for now enjoy the grossness.



With the wheels off, let's break them down and see what we've got. The front wheel was bent, both wheels were missing spokes, and the spokes that were left were so seized that many needed to be cut off! There were stripped rotor and sprocket bolts, but those were removed by welding on a fresh nut with the MIG.






These bearings sure look awesome!

[Slick_Nick]

Bearings bearings, everywhere. Working on pulling apart the swingarm, of course everything will be replaced, but lots of the hardware was stripped out and gross.





For triple clamps, I've always found that the easiest way to get the lower bearing off was just to press the entire stem right out of the clamp. Since I'll be doing some fresh Cerakote on these, the stem had to come out anyways.

[Slick_Nick]

It's engine time! What suprises do we have in store? Let's find out! Threw some plywood down on the bench. I didn't have an engine stand at this point, but I do now.







A lot of these photos don't really need much comment, just the engine through various stages of disassembly. Parts were all laid out on a service cart so they can be cleaned and cataloged. With the head off, I could see there was new-ish Vertex forged piston installed. The cylinder plating looked in decent shape, I will measure the cylinder later.




The clutch plates looked pretty good, they actually measured out almost brand new! I'll be saving these for a spare set.

[Slick_Nick]

Right side completely stripped down, save for a few stripped philips screws which I will remove with the welder.



Moving over to the left side, looks like maybe something broke a small piece of this casting that holds the chain guide at one point.



Cases split, the crankshaft has a pretty neat staining pattern on it.




The KX250F has two internal oil screens, one for each half of the oil pump in it's semi-dry sump lubrication system. As far as I could tell this was the factory bottom end, it had never been disassembled before. As the pickup screens show, this engine has seen some carnage at some point in it's life.




I find that it's easiest to lay everything out in little groups on a service cart, so I can wheel it all over to the solvent tank, and inspect and bag everything once it's cleaned off.

[Slick_Nick]

Upon closer inspection of the piston, it looks like this one may have kissed the valves at one point. Maybe that's the reason for the new cylinder head?



Let's tear down the head so we can clean and inspect it.





Once the head was cleaned in the solvent tank and dried, I hit it with a super soft glass bead in my blast cabinet. This easily removes all carbon, but won't harm things like valve seats. Use care to blow out every tiny nook, cranny, oil passage, water jacket, with compressed air. Then, do it again. Then, do it some more, until not a single glass bead remains. Then, wash the head with soapy water, and repeat the last three steps again.




You absolutely CAN NOT lap titanium valves! I did, however, green them up, and double check that the contact patch was good.

[Slick_Nick]

With the rest of the aluminum bits freshly dried out of the solvent tank, into the glass bead cabinet they went to bring back that factory shine. (Old vs. new)








With all the blasting done, I wanted to spend some time outside, so figured I'd use an aluminum etching cleaner to bring this frame back to life. The frame itself had no cracks and I smoothed out some of the bigger scratches and dents with a scotch wheel. The 2006 frame is unique in that it was the only year of this generation ('06-'08) to have the two "stripes" on the upper tube section.

[Slick_Nick]

Gratuitous glamour shots of the frame, swingarm, and subframe!

[Slick_Nick]

Brought back inside. The aluminum brightener is phenomenal. It leaves a super bright, almost "white" finish if that makes sense.




The floor is no place for a frame like that, but in order to get it back onto my lift stand, we need some foot pegs. As I'm going for more of a "factory restoration", I decided to refurbish the foot pegs in their stock black color. I'm not sure if they are plated or painted from the factory, but I decided to zinc plate them, and the use an oxide blackener to get the effect so it will be very durable. I went with yellow chromate for the springs because, that's how the stock ones are. After bead blasting to a matte finish, here are the plated parts.






Fancy pegs installed:

[Slick_Nick]

With the frame back on the stand, we now have a clean, blank canvas to work with as we build this back up from a "bike in a box" to its former glory.





Since I already had a majority of my new parts in, I wanted to get everything cleaned, organized, and prepped as much as I could, so that the final assembly would happen quickly. Things were completely broken down, cleaned, bead blasted where required, inspected, replated, and organized so that they were ready to assemble and easily at hand. I find that breaking things down into "sub-assemblies" is a great way to stay organized and ahead of the game.

The petcocks on these bikes have a habit of collapsing. I was able to source a new one. I also sourced a used rear caliper mount, as this one was destroyed and unsafe. More on the assembly of these things later.

[SS109]

Dude, I love it! I have an '06 chassis that's been waiting forever to be converted in to an AF conversion. I actually pirated the forks to put on my KDX! Seeing how nice you got that frame and the other parts makes me want to get back to it but, sadly, I'm too deep in a lot of projects right now.

Keep the updates coming!

[Slick_Nick]

Various assemblies continued to be torn down, cleaned, and inspected, before being catalogued. Take this brake assembly for example. This is why I enjoy doing all of my own work in house. I can make ready, new hardware without having to send things away and wait weeks to get them back from refinishing.





The front caliper looked roached, but look after a few minutes work, good as new.





Remember the disgusting axles and swingarm bolt? They were cleaned, blasted, and replated.




Much better!

[Slick_Nick]

2006 models had silver rims and silver hubs, 2007 models had silver rims and bronze hubs, and 2008 had black rims and bronze hubs. While I paused for a minute, giving how well the stock '06 wheel hubs cleaned up in their bare aluminum state, I really liked the look of the wheels that the '07s came with, so they would be Cerakoted instead.



More parts blasted, and into a burnt bronze Cerakote. The color on the triple clamps is the same as the engine covers, it's just the interior lighting in my kitchen making them look so much lighter!






This bike came with Enzo suspension on it, I won't know until later on if it's set up for me or not, but I was able to see the stamp on the shock spring, and it was actually the correct one for my weight! Score! After it was blasted, I gave it a coat of Kawasaki green.




Before / during / after replating all of the hardware. In this case, it's the kickstart boss and stuff.

[Slick_Nick]

Replating hardware can sure be tedious, but man, are the end results ever worth it. Enjoy some gratuitous shots of my DIY zinc plating.







Recall how crusty the stock water outlet was? First it was zinc plated, then I used the blackener again just like the footpegs to give it that factory black look.





Also did the same with the shifter tip:

[Slick_Nick]

The exhaust. Oh the exhaust. Such a sweet unit! But its disgusting, and bent from when someone wheelied just a little too far. Let's get this titanium jewlery cleaned up and refurbished! There was zero packing left.




Cleaned up beautifully!



Bad news, however, the can was cracked at the mounting tab, and so was the mount for the midpipe.




Well, I've never welded Titanium before, but I gotta say, for my first attempt, it sure is fun! The filler rod is astronomically expensive, but cheaper than taking it to a shop I guess!

[Slick_Nick]

Freshly repacked and she's good as new! Well, not new, but considering this exhaust is now discontinued, it'll have to do!




I wasn't going to bother keeping that stock crank, I didn't know it's history, but lets check it anyway.



Rebuilding the crank with a fresh Pro-X rod kit and truing it up!






Got the runout to about half a thou, well within spec! She feels great!



I have no idea why the crank has that oil pattern or whatever like that, I've never seen that before, I tried everything under the sun to remove it, including a weekend soak in the solvent tank, thinner, lye, you name it. Oh well, give it cheetah power I suppose?

[Slick_Nick]

At this point, I basically had a bike in a box. All the hardware was cleaned, every last bolt was replated, parts were all ordered and all arrived, I had everything Cerakoted and refinished that needed it. New Kawasaki parts (where needed) were in hand, and most importantly, I had everything (except the forks) broken down, checked, and catalogued. I am pretty meticulous when it comes to how I do stuff, once I get going on a project, I hate having to wait on parts, or realizing that something was missing or broken. So, I cleared out a section of the shop, buit a makeshift table to temporarily keep things organized while I built, and I laid everything out to do one final comparison to my lists and make sure I had everything.

Behold, my exploded bike.

[Slick_Nick]

[Slick_Nick]

All those parts sure are fun to look at, but they're no good just sitting there. Where to start? I figured the engine was as good a place as any. Might as well get the cylinder head together. Head is milled completely flat, did the same with the case halves as well as the cylinder, which by the way I checked with my bore gauge, and it's within spec. Honed with a proper Nikasil hone as well.



Gave the head one more bath in soapy water and a dry off with compressed air so it was spotless.





With the head done, all of the transmission components were inspected, lubed, and assembled onto their shafts.




With the cases washed once more, ALL bearings were replaced with OEM Kawasaki units. They are expensive.





Just awaiting the guts: