KX 125 Re-Build – The Ugly Duckling


coverIn our August / September issue of Eastern Dirt Magazine we showed you how anyone can get into Off-Road with a relatively small investment. For the small sum of $1500.00 we bought a bike and gear. From AXO we bought a helmet, boots, gloves, jersey, and pants. We also purchased a ramp, gas can, tie-downs and an owner’s manual on what seems an impossibly small budget in today’s motorcycle market. If you did the same thing, you’ve probably had enough time to decide if you like riding or not. If you are anything like us, you don’t just like riding. You love riding and you’re hooked.

At your local riding area you probably met some other guys who are riding at or around your skill level and you’ve got a small group of riding buddies that plans to meet at the track /riding area every available weekend or weekday if you are one of the lucky ones. These friendships have a way of growing, you might have hung out with one or two of them away from the riding. It seems that most dirt bike people are very friendly and enjoy hanging around like-minded people.

Talking motorcycles is just as important as riding them, more so to some. Be careful not to get cornered by one at your local dealer! It is also likely you have met or will meet someone who is more proficient with a wrench than you, someone who can give you a hand in the mechanical department once in a while. (We love working on bikes and are always willing to give a hand). At this point you may have done some tinkering on your bike. Perhaps you followed one of our Tech Tips articles and sorted out your chain slack adjustment or serviced your fork.

IMG_7123It’s a good thing we bought the owner’s manual with our remaining money, hopefully you did too, after a couple months thrashing on the little KX that could, it needed some serious attention. Pressurized coolant was leaking through the water pump shaft seal into the oil. The bike had no power thanks to a loose piston with cracks on the skirt. The KIPS power valve was so full of carbon it barely moved. And the clutch was sticking so badly in order to shift into first gear with the bike stopped the motor had to be hot. These were the obvious problems. Are you getting the picture? Our KX was in need of serious attention.

For this featured article, we thought we’d go through the KX and give it the once over, maybe even replace a few parts that are giving us the shakes. If your bike is anything like ours, it is feeling a little loose in a lot of places. Our KX is really bad.

When we originally started this project we thought we’d just do what was needed to keep the KX rideable, a new top end, fork seals, wheel bearings, and service the swing arm link, nothing major. With this in mind, we started with a call to All Balls Racing for some bearings. They make replacement bearings for the hubs, headset, fork seals and bushings, and everything you need to completely rebuild your swing arm and linkage, including the oil seal for the rear shock. They even have crank bearings. We wound up ordering everything they made for the KX.

Realizing how much effort was going to go into replacing all the bearings, our KX project took a nasty turn, we decided to go through it and completely rebuild it with all the aftermarket part we could find, there are many.

IMG_7129With new crank bearings in hand we knew we would be splitting the cases, a call to our friends at Mac Tools was necessary for a universal case splitter. While we had them on the phone we also ordered a slide hammer to pull hub bearings, a Motion Pro clutch basket holder and torque wrench adapter for the impossible to reach nuts that hold the cylinder on. We called on Wiseco for some top end parts and while talking with Al Pizzino, he informed us that they have complete bottom end kits, including crank, connecting rod and main bearing. Since we already had the main bearing set from All Balls we didn’t need it but ordered everything else Wiseco had to fit the KX. Al was also kind enough to hook the KX up with a new clutch basket, the old one was toast. Plus a black anodized, billet clutch cover, these rate very high on the cool factor scale. We also ordered a piston kit, what motor rebuild would be complete without a Wiseco top end?


Underneath the clutch cover, Barnett clutch disks and plates will be handling the dissemination of power. Knowing that the KX was weak in the bottom end we called Boyesen Engineering for some help from their Rad Valve – reed block. Boyesen also makes beautiful clutch and ignition covers, we opted for the black ignition cover and we are glad we did. The KX motor will go together with a gasket kit from Cometic. Dirt and debris will be removed from the air by passing through a No Toil air filter.

With our motor and rear shock out of the frame we thought it would be in our best interest to ask for help. Considering the amount of work we had with the rest of the bike waiting for us. Who better to ask for help than Chad Watts of Watts Perfections? In 1996 he wrenched for Supercross East #1 plate winner Mickael Pichon riding none other than a KX 125. In 1997 he began the era of the GOAT, Ricky Charmicahael. The point is, he knows this motor inside out, upside down and sideways. Chad was kind enough to lend his skills to install the new connecting rod on the stock crank and rebuild the rear shock. The side play on the crank was way past the point of no return. The specified tolerance range is .40-.50, the service limit is .70 ours was .80.

Crank rebuilding is a very special art that requires special tools and a crazy dance for the crank gods. It should be left to a pro. Or go the smart route and buy a complete kit, crank and rod. This way you can assemble the motor without the need of help from someone like Chad.

With the motor parts on order we turned our attention to the rest of the bike. The swing arm pivot and linkage was in a state, a total nightmare! It was as if it had not been serviced once since it was originally purchased. Several of the pivot points were frozen solid with dry, rusty needle bearings, nice. The bearing for the lower shock mount actually ground the needle bearings into tiny little bits. We had to use a grinder to get the steel race out. Needless to say it was a boatload of work. If you don’t service your rear shock linkage, it will come back to haunt you! Or someone else, as it did in our case.

The All Balls Racing bearing kits work very well as OEM replacements. Pressing out the steel bearing race was a major PIA made much easier by the Motion Pro Bearing press tool. A must have if you are planning to replaces these parts. After installation of all the parts, the swing arm pivot area felt like new again and brought a smile to all who felt it before we did the work. With routine maintenance it will continue to perform as intended.

IMG_7177With so many new parts going into the motor and a sweet feeling swing arm linkage our KX was feeling as if it found the fountain of youth. Feeling so young and fresh but still having a head full of gray hair wouldn’t work. A new plastic kit was in order! We called UFO Plastic, the number one choice in aftermarket plastic and spoke with Mark to see what they had available, he was a great help. Turns out they make everything except the air box. We ordered it all. With new plastic on the way the thought of installing it on a scratched and worn frame just didn’t seem right. The few remaining parts came off and we took the frame and sub frame to R&R Powder Coating for a fresh coat of Kawasaki green. These guys are fantastic, quick turnaround, an amazing selection of colors, matt or glossy and metallic. The big thing is they do small runs. They also do large pieces, they were powder coating a frame from a car restoration while we were there. It’s a pretty impressive place and they are very friendly. To keep our frame rails looking good we contacted Works Connection for a set of frame guards and a glide plate. Both mounted with ease and looked awesome.

IMG_8131In order to keep with the “make it feel new” theme, we had some other parts that needed to be replaced. The shift lever for example was so stripped that no matter how much we tightened the sinch bolt it still would not change gears, it just spun around. Sunline was the obvious choice for a replacement. Their aluminum shift lever fits perfectly and looks works-bike sweet. They also make an anti-vibration handle bar that we couldn’t resist, the AV ONE. It reduces vibration over conventional bars by 40%. Plus it comes with a bar pad and dual compound grips. The grips are the best we’ve seen, buy some today, you’ll be glad you did.

kxrightleverWith a new bar and grips we couldn’t handle the sight of the old, stock levers and broken throttle body. A call to Bob Morales at ASV Inventions for a set of their F3 series unbreakable levers got us going in the right direction. These levers are well worth the cost. They provide such incredibly precise adjustment of the lever to bar relationship that any hand, big or small will feel comfortable using them.

When we think of throttle body replacement, Motion Pro comes to mind. While we were on the phone we also ordered a T2 clutch cable and throttle cable in Gray. We now have a bar and controls that look and feel current, not to mention extremely trick.

kxrearbrakeThe stock brake lines did not fit in this picture. A call to Galfer USA was the only thing to do. Steel braided brake lines make for much better brake feel and the look ads to the custom feel of our KX. We also picked up a rear disk, ours was well past its service life.

With these parts looking as sweet as they do our triple clamps started looking very dull. The obvious solution was to bead blast them. We removed all the aluminum parts from the triple clamps to the swing arm and bead blasted them, making them look brand new again. There is no other way to get years of caked on mud and clay from these parts. Believe us we tried everything from simple green to oven cleaner. Nothing worked. Bead blasting is the answer. You can see our cylinder half dirty and half clean for proof.

The KX rims simply could not be saved. They were wobbly, scratched, dented and cracked. Plus the spokes looked like they were found at the bottom of the ocean, rusted, corroded, and nasty. Replacing rims is a relatively easy process, if the spoke nipples turn. Contact Park Tools for a truing stand, they make the stand we use, it works great and it will give you years of service. For rims and spokes we called Jason at Warp 9 Racing. Black anodized rims and heavy duty stainless steel spokes were the direction we wanted to go. They sell complete wheel sets as well as rim/ spoke sets. It was the right thing to do. Green and black go together like Carey Hart and Pink. The hubs got the bead blast treatment and new bearings dropped in. Then we laced the wheels, with some help from our shop girl Sara. Look for our Tech Tip on wheel building with this LINK. Both wheels went together smoothly with the Warp 9 rims and they look fantastic. We finished off our wheels with a set of Kenda Millville tires, perfect for the intermediate conditions this time of year.

IMG_8136Since we had black rims, bars and levers we decided to continue the black theme and called on Noam at Driven Racing for their aluminum sprocket and chain kit. Their kits are available for MX as well as Road applications. The finish is stunning and the countershaft sprocket is black too. Keeping the KX’s chain on track will be the job of TM Design Works Chain slider and Chain block. The old one had so much wear the chain cut the bolts in half! People, service your bikes!

With all of these new parts making the EDM KX look super fresh the nuts and bolts were looking a bit shabby. And while shabby can be sheik it looked like crap on our KX. We called Tekbolt and ordered their double MX-J1 Japanese 1990’s Pro Kit which provided the nuts bolts and washers to replace all the tarnished original hardware. These kits are fantastic and a great thing to have around even if you are not doing a complete rebuild. You never know when a nut or bolt is going to rattle off and end your day of riding early.

Footrests are vital to the feel of your bike, and Pro Moto Billet foot pegs make this connection perfectly. We chose to go with the F5 pegs and with the Evolution II F6 replacement cleats there is no chance your feet will slip off. Check the photo, these are serious foot pegs!

Finishing off the project we turned to Jason at Ride PG Graphics for a custom graphics kit. They gave us so many options our head was spinning! Plus they helped us fit all the sponsors for this project into the available spaces. We think they did a great job! We finished it off with a black gripper seat cove from Factory FX.


You may be asking yourself, why put all these parts on such an old bike? Here’s one answer: for $3,750.00 we have a basically brand new, completely custom KX 125 which is just over ½ the cost of a brand new bike that anyone can have by walking into a dealer. Oh wait, Kawasaki doesn’t sell the KX125 in the US anymore.

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