by J. Rex Brown
"So how fast does your dirt bike go?"
It’s an inevitable question, most often posed by the uninitiated. But most dirt bikes don’t have speedometers.
After selling my KDX200 I really missed having an odometer. Most off-road enthusiasts don’t seem to care that much. But I always found the odo to be… well, interesting one way or another. I mean, it depends on the situation. Sometimes you look down and think: Jeez- we’ve only gone 8 MILES!?! But on a good day, a glance at your odometer is good for an instant `Atta Boy.
I hadn’t really given much thought to putting an odo on my KX250 until I bumped into a fellow at Lake Draper. He had a digital readout on the handlebar that, at first glance, looked like a wristwatch without the strap. Indeed it did tell the time, along with a great deal more. It was a bicycle computer.
To get the story on these bicycle computers I checked with Tom Brown at River Trail Bicycles in Tulsa. He had a selection of different models ranging from $20 to $100 in stock. I was concerned if they could be adapted to motorcycle use since they are calibrated to the circumference of the vehicle’s tire. As it turns out the factory setting is almost perfect for a 21" motorcycle wheel.
Tom’s recommendation was the Cateye Enduro. Cateye produces a wide range of electrical bicycle accessories. This particular model sports a much more substantial cable connecting the pickup unit to the display- an important consideration. Most of the other units come with something on the order of automotive speaker wire. The digital display is water-resistant, and large buttons make it easy to reset or adjust. The main readout shows your current speed whenever the bike is in motion. The lower portion of the display shows your distance, riding time, average speed, maximum speed or overall distance. All of this in vivid liquid crystal gray for less than thirty bucks… and it comes with a clock!
The pickup unit is a sensor that detects the passing of a small magnet with each revolution of the motorcycle’s wheel. A molded cable connects the pickup to a bracket that clamps on to the handlebars. The digital display snaps onto this bracket when in use. For storage or washing, it easily pops back out. The magnet is mounted somewhere on the wheel that will be on line with the pickup assembly. A watch battery in the display makes all this fancy stuff work.
We now have two of these installed and undergoing "field tests". One is mounted on a 1994 Kawasaki KX250 and the other is on a 1996 Suzuki RM125. The photos show the installation on the KX. If you have any interest in mounting one of these to your bike read on…
Unfortunately, the cable supplied with the Cateye Enduro is not long enough for most motorcycle applications. On a bike with inverted forks you will need to lengthen the wire about a foot, unless you are extremely creative with the mounting of the pickup. In my search for suitable wire that could handle the abuse of the trail, I ended up splicing in a section of wire from a dead computer mouse. After routing my extended wiring alongside the front brake hose I was ready for the fun part, mounting the pickup!
Each bike will be a little different in this department. On the KX there is a convenient bracket that retains the front brake hose. After tweaking this bracket and drilling a small hole the pickup unit was mounted. The only other modification involved was a little carving on the fork protector bracket. At full compression this bracket can smack the end right off the sensor. That small annoyance aside, this location is ideal since the caliper and fork leg protects the pickup and cable from debris.
The approach was a little different on the RM125 because of the conventional forks. As it turned out the front disc guard provided a perfect place to mount the pickup sensor. After drilling a small hole in the guard the pickup was mounted in a matter of minutes.
Finally, attach the magnet to the wheel or brake rotor and you’re done. On the RM the magnet supplied with the Cateye is simply attached to the brake rotor. On the KX I took advantage of the large rivets that hold the brake rotor together. The magnet was mounted using a nylon bushing and push-on cap from the hardware store, some two-part epoxy and a rare earth magnet from Radio Shack. The result is a clean installation that is durable and trail worthy.
Now when people ask, "how fast does it go?" I can take a quick peek and tell them. Actually the most beneficial feature I have discovered so far is the Average Speed setting. Whenever I want to improve my times I go out and find a challenging loop. Check the Average Speed after a run, then reset the unit. Make the same loop and check the Average Speed again to look for improvement. Increasing this figure by just a couple of MPH can be a real accomplishment!
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