I'm running the motard set up, 17" wheels, and my speed reading is out a lot (fast).
By my rough calculations it appears that the difference between actual and real (checked with my car) is consistant with the difference in wheel circumference between 17" motard and 21" offroad wheels.
Can anyone confirm the speed sensor is different for each wheel size?
I'm not sure how this sensor works, I think there is a magnet inside it?

If anyone else has both set ups, how do you solve this problem?

Thanks

 

The shorter the tire the faster it thinks its going. spinning a 21" tire at X rpm will be going faster than the 17" at the same rpms.

The speedo thinks you still have the 21" on

 

use a gps...

 

Since the stock speedo on a stock bike is out by quite a bit, this is good advice and the easiest solution. The sensor at the hub just sends a signal to the computer in the speedo head and that where the problem is. I don't think that even a dealer can re-calibrate it. See if you can borrow a GPS for a day and re-calibrate your reading of the speedo. On mine I know that a reading of 55 is actual 50; on mine it has a consistent 10% overindication.

 

MPH = EngineRPM / overallRatio * (TireCircumference/12) * 60/5280

Assuming your gearing ratio didn't change, your

(3.14*17)/12 =4.448
(3.14*21)/12=5.495

Your speed will be off by a factor of about 1.2. The speedo is calibrated for the 21" tire, the 17" tire has to spin 1.2 times faster to maintain the same speed as the 21".

I think the speedo is not magnetic (at least on the '07), it is a series of gears. Borischan, what year KLX you have, the one with the analog tach or the digital tach?

If it is magnetic (most likely the digital one is), you'd have to recalibrate the brain of the display for the amount of pulses/rev to MPH. In short, just use a GPS, it would be much easier, or if you know how much MPH you are off just keep that in mind when driving

 

Yeah, I know that.
What I don't know is if I have the wrong speedo, or wrong speed sensor.
Motard and off road versions are basically the same bike, I'm trying to find out how Kawasaki compensated for this. I'll try to search part numbers...

jxg... thanks, but I'm looking for a $20 fix, not $200

PSUdude85...
Thats pretty close to my calculations, and real data. I did a run in my car, and then my bike, distance covered by bike was around 20% higher. 5.5km car/6.7km bike.
My bike is a 2003, digital meter, so the sensor has a magnet inside although I haven't taken it apart to check it. I know I can get a used sensor cheap (lots of used parts here in Japan)
I'm recording too much mileage at the moment, so did the last owner...haha
I'd like to get a more accurate reading, but on the plus side, top speed is impressive!!

 

actually, if you fleabay an old handheld (like a garmin gps 12) that doesn't do mapping, just coordinates, speed, etc, you can get them for under 50 bucks sometimes. I even bought my daughter a TomTOM 1 (which does do mapping) brand new at staples for $70.

just sayin...

 

Yes, add $50 to send to Japan......then wonder why my town isn't on a TomTom map
I'm searching Japanese sites now, headache trying to read that stuff.
Most people go with aftermarket meter, I'll get a suitable sensor and/or used speedometer.

Or stick my iPhone on the handlebars..

 

Update:
This product will work, according to the company.
http://www.12oclocklabs.com/

Hoped for a cheaper solution, but dollar is weak now

 

The faster you go the more its off. At lower speeds its just a few MPH. Then, like mentioned above, at 55 its really 50. I know when you hit 90 MPH your really going like 82 MPH