How-To: KX250F / RMZ Top & Bottom Engine Rebuild


Year, Make, Model

A 2006 Kawasaki KX250F is featured in this rebuild video.

Video applies to the following makes and models:

2004-2006 KXF & RMZ 250 (identical engines)
2004-2017 KXF & RMZ 250’s (very similar)

Symptoms & Diagnosis

I covered the symptoms and diagnosis in an earlier post here. Basically, the shifter detent pin boss in case cracked and was not allowing the shifter to “spring” back to its neutral position.

Below is the video which shows removal of the RH case, and part 1 of this video series picks up where this video left off.

Tools

Here is a list of all the special tools used in these videos available from Amazon.

Motion Pro 08-0008 Clutch Holding Tool

Tusk Crank Puller/Installer Tool

Tusk Crank Case Splitter Tool

Motion Pro 08-0026 Flywheel Puller M27X1.0 L.H External Thread

Motion Pro (08-0427) 4.9″ Gear Jammer Tool (optional, not needed if using air tools)

Parts Used

I used OEM parts for this project, however you can save some money by going aftermarket (all available from Amazon).

Hot Rods CBK0028 Bottom End Kit

Hot Rods WPK0036 Water Pump Kit

Cometic Gasket Bottom End Gasket Kit C3354

Cometic Gasket EST Top End Gasket Kit – 77mm Bore C3174-EST

How-To Videos: (Part 1) Disassembly

Here is my poor attempt of being organized. Make sure to have ziploc bags and a sharpie handy for all small components. Part 1 of this video series is located at the top of this page.

2006 Kawasaki KX250F Top Bottom Engine Rebuild 1

How-To Video:  (Part 2) Assembly

Part 2 is available through Gumroad. The video is available for streaming only. Length: 143 minutes! If your not happy with the video purchase, just ask me for a refund, no questions asked!

What Does Part 2 cover?

  • Removing and installing bearings without special tools
  • Installing new top end (piston and rings)
  • Installing new cam chain and timing procedure
  • Valve clearance check & adjustment (I have a more detailed video here)
  • Any special tools used
  • Piston ring end gap
  • Replacing water pump bearings and seals

What Part 2 Does Not Cover:

  • Cylinder head was not dis-assembled, it was removed and re-installed
  • Removing & installing engine from frame

Save Money, Fix It Yourself!

A shop will easily charge $500 for a job this size. I completed this rebuild in my home garage with basic hand and some special tools. The FREE service manual and these videos will help you save money.

How-To Video:  (Part 3) Start up, Tuning Fuel Screw, Test Spin

The best part of any big project such as this one, is the first start up. The bike fired up on the first kick! No it was not staged! You’ll notice that I like to give the throttle a quick twist or 2 before kicking to have the accelerator pump squirt some fuel down intake port.

As you can see during the test spin portion, the throttle response is amazing now ! If you whack the throttle, the bike will wheelie and flip you over! I took a peek in this carb during the rebuilt and cover the jetting changes made here.

Comments

Please comment below if these videos have helped you out.

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45 Comments

  1. Hello, was really hoping you can share with me the things you did to tune and to get the response you got from the carb. I have a 2010 of this model and have done the o-ring mod you showed, but would like some more throttle response. Thanks!

    • Ryan,

      When I opened up this carb, the jetting was off. The throttle response was improved by jetting and tuning the accelerator pump circuit. O-ring mod, 45 leak jet, and adjusting the pump timing to where the squirt just misses the slide. I turned the timing screw CCW to advance the timing for an earlier squirt.

      Keep in mind that the only reason I modified the pump timing is because someone adjusted it to the point where the screw almost fell out. If you adjust yours, count the turns so you can always go back to stock.

      To summarize, o-ring mod and 45 leak jet will probably get you the throttle response you need.

      Let me know if you need any more help.

  2. You really know your stuff! I’ve already learned some tricks from the first 20 minutes of watching part 2. (The grill trick is awesome!) Easily worth the $14 to save time and money by learning how to do the rebuild before I attempt one myself. Thanks!!

    • Thanks, Jared. Trust me, your mom/girlfriend/wife may only let you stick an engine case in the oven one time. After that, you’ll have to figure out another way.

      Let me know how the other 120min go.

  3. Hey Matt,
    I have used your videos to rebuild a CR250F and they were a huge help. Do you have any on a top and bottom end for a KTM SXF 250? Have to do my nephews.

  4. matthew, yesterday when i was driving my crf450x, the chain came off and hit in the shift pedal. unbelievebel, happened the sam problem that your kx250f….. the shift pedal goes up but dont came down…. i think that i have to do the same rebuild that you do in this kx250f….wish me luck…it is the first for me 🙂

  5. I love all your how to videos. If not for you or these videos I wouldn’t be able to afford to ride a dirt bike. Your videos are very helpful. Thanx Matt for doing what you do.

    • Thanks, Joe!

      I’m with you on how to afford this hobby. It wouldn’t be possible if I had to pay for repairs.

  6. On the gopro vid of you riding up and down the street on the kx250F I noticed a lot of decel popping. Shouldn’t the fuel screw be opened up a bit to top the popping?

  7. Matt, I own an 07 KX250F and used your top end rebuild video to adjust my valves. Your video was by far the best on the internet…… Thanks a bunch! I also had the head cleaned and valves reseated at a machine shop. After putting it back together the motor idles great, pulls hard and starts fairly easily. However, she seems to sputter a little when you initially take off and I’ve got a little popping from the exhaust when you let off the throttle. Any ideas?

    • Hi Mike,

      First off, make sure there are no vaccum leaks or exhaust leaks. Next, I would focus on fuel screw tuning. Let me know what pilot jet you have and how many turns out you are on the fuel screw.

      • Matt…. Sorry so late in responding. I had to work late every night this week. I took the carb apart and found the following jets…… 170 main, 68 starter, 42 pilot and 50 leak jet. One of things I noted was the diaphragm under the starter cover was deteriorating. I’m not sure if that would cause the spitting, but I’ve got one on order.

        One thing worth noting…. The bike is pretty much stock other than a K&N filter. Stock exhaust, stock header pipe and I live near sea level. I do have a slight exhaust leak where the muffle and header pipe meet. I’m going to seal that up today. Hope this info helps.

  8. Paul Knapp

    hi mate I have a kx250f 2012 will your how to be on for that year?

  9. Jarrett Grantham

    Matthew, does video 2 cover pressing in new kickstarter idler pin into the new engine cases? That is one thing that I don’t see the service manual covering and I’m just curious as to how you did that.

    • Yes. New cases did not come with that part installed, so I had to remove from old cases and install in new case.

  10. Service manual like doesn’t seem to be working. Do you have any insight to a new link?

  11. Mattew,
    I have a 2010 KX250F. I have tore the engine completely down and now I’m having trouble getting it back together. I’ve replaced the crank due to the rod being bent when the engine grenaded. Valves broke as well so top end is tore down.. Does part 2 of 3 show me everything I need to be able to get the bottom end back together. This is my rebuild of this level so the more help the better.

  12. hello, will these videos work for a kx450 2010?

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