2009 KLX 250s Supermoto Conversion

So you want to go from this -

To this ??

Well, you'll need a few things.  The easiest method for converting a 09+ KLX250S to supermoto status is to acquire a set of KLX250SF wheels.  You can find them on ebay (as i did) or buy them new from a factory Kawasaki parts dealer (~$1200 when i checked in 2012) or get lucky and find a deal on a forum or craigslist.

The nice thing about the SF rims is that the hubs are the same as the S wheels so actually mounting the wheels up will be a straight swap with the factory axles and spacers.

Now assuming your wheels came complete with rotors and sprockets (and that they are usable) the only requirement to fit the SF wheel will be the larger front caliper mounting bracket that will need to be installed to allow clearance for the larger SF rotor.  I covered this in my SF front brake conversion post here.  This can be purchased via the same channels you can get the wheels from.  The rear wheel needs no extra attention and will fit right.

If you just got the wheels you will need to swap out your old S rotors to your new wheels, this is what i had originally done on my bike and saves the need to swap out the front caliper bracket since you are reusing your existing rotor.  I found this setup to be entirely satisfactory and would not have bothered "upgrading" the front except for the fact that a smoking deal fell into my lap for an SF bracket and rotor.

Now that the fitment issues regarding the brake have been taken care of, the next issue is the gearing.  The S model with its larger 18" rear wheel and 42 tooth rear sprocket will experience a significant decline in final drive ratio with the smaller 17" rear wheel.  The best method to rectify this is to get a 39 tooth SF rear sprocket, though you can achieve nearly the same end gear ratio with a larger 15 tooth front sprocket.  (Note that the 15T is the largest front you can run with the stock case saver in place).

Hopefully now you've got your gearing sorted and the bike will have a top speed of more that 60 :)

Next we have to tackle the unfortunate reality that since we've now gone from a 21" front wheel to a 17" wheel the speedometer is now WAY off since the instrument cluster calculates speed based on revolutions of the front wheel. ( new smaller wheel will rotate more times going the same speed).  In my case the bike was reading ~90 while the GPS i had taped to the mirror was telling me i was going 60.

The solution i used was the 12 o'clock labs SpeedoDRD  -http://shop.12oclocklabs.com/index.php?route=product/product&product_id=59

You'll want the Y1 model for the 09+ KLX250.  $79.99 as of time of this article. ( I have no affiliation with 12 o'clock labs BTW).

The other option for the factory dash are the Speedo Healer that you can get from Blue Monkey Motorsports which I believe are $116.  I'm not sure what model you need as i went with the speedoDRD.

If you want to go fully custom, there are various aftermarket instrument clusters available with the Trailtech Vapor being one of the most popular for the KLX - http://www.trailtech.net/digital-gauges/vapor This solution however will require custom wiring for most all of the dash functions.

And that should be all you need to get your Tard 'on with your KLX.   If you want to swap back and forth between dirt wheels and sumo wheels i would recommend having two sets of rotors (one for each wheel) as well as standardizing the front rotor size so you don't have to mess with switching the caliper bracket each time, which is probably the hardest part of the wheel swap.

Happy motoring !

KLX 250 Rectifier ground mod - possible fix for ~6500 RPM stumble

This is an archive of the relevant information regarding the rectifier grounding mod that was discussed over at the Kawasaki forums pertaining to a fix for the stumble or miss that affected some KLX 250's at around 6500 RPM cruising speed.

Special thanks to Maine250SF for reporting his experiences with Kawasaki warranty work which is where most of the information on how the mod is to be performed and to David R for confirming an actual electrical anomaly with his diagnostic equipment.  The original thread can be viewed in its entirety here - http://www.kawasakiforums.com/forum/klx-250s-71/surge-6500-rpm-highway-speed-34470/


Basically the mod entails either cutting and re-grounding the black/yellow wire pictured here that runs from the regulator/rectifier to the existing factory ground, or splicing into this wire and adding an additional grounding path.   Most use the starter motor ground located just to the front of the rectifier plug as seen in the pictures of my modded ground below David's quoted post from the forum.


David R - post # 65 from http://www.kawasakiforums.com/forum/klx-250s-71/surge-6500-rpm-highway-speed-34470/

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This is the plug.

BLACK WIRE WITH YELLOW TRACER

I made my ground "T" in with the ground already there.  Its a ground in parallel.  Crimp on terminal on the other end of the wire and bolted to the engine using the existing bolt going to the same spot as another ground already on the motor just in front of the reg/rec.

I want this clear.  I soldered a wire to the back part of the terminal you see in the picture and inserted the terminal back into the plug.  Plugged it back in.  Motorcycle wiring was not changed, cut or removed only extra ground added.
This is what I was getting occasionally

This is more like what it should be

I ran the bike for a few minutes after doing the repair and saw only normal spark traces.  I am going to check the grounds to the CD box and coil.

40 miles, and I THINK its fixed.   This inculded an attempt to do 80 on an expressway.   Pavement is grooved and enough traffic that the bike was not too stable so I backed off to 70-75 mph.  It seems to run great.

David

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Here is a picture of the finished mod on my bike.   Remember to make sure if you are cutting the wire to ground the plug end of the wire that is attached to the white box that plugs into the rectifier and not the end that runs into the wiring harness with the other wires to the original ground.  Grounding the wrong end will result in your battery not being charged and eventually the drained battery will cause the bike to die on you.