Digital Speedo on da Cheap

Since I've been traveling further distances with my Puch in Japan, I needed an odometer to keep track of my mileage (or in my case kilometers).  I also needed to keep track of my speeds since in Japan, the law states the max speed your allowed to go depends on your engine's displacement.  I registered my Maxi as a 75cc because of my Gila kit.  So I'm allowed to go a maximum speed of 60 km/h.  That's only 37.28 mph!!!  If I registered it as a 50cc, I would only be allowed to go a maximum speed of 30 km/h (18.64 mph)!!!




I wanted a cheap speedometer/odometer.  I'm eventually going to replace my whole speedometer system with the Trail Tech Vapor when I replace my whole front end for a disc brake setup.  So for now, I needed something to keep me legit.  I scoured Moped Army forums to see which cheap alternative is working best for everyone.  I decided to try this one:

Made In China

I ordered it on Ebay for $8.99 with shipping .  It's solar and obviously made for a bicycle.  It comes with:

The computer unit

Base that mounts to the handlebar

Magnetic sensor

Magnet with spoke attachment

 I kind of ghetto rigged it since it's only going to be temporary.

Ghetto fab stereo bracket

Ghetto rigged the magnet sensor to the bracket with tie straps that came with the kit.

Ghetto rigged the base plate to the handlebar with tie straps that came with the kit.  I had to loosen the handlebar clamps in order to lift and slip the tie straps underneath the bar.  The stock speedometer still works but is mainly there to keep my moped "appearing" legal in Japan.  Besides, the 30 mph limit is pretty much useless.

I installed the magnet on my star rim.  I only used the magnet side of the mount.  The mount was slotted in the back so I used it to attach to the star.  Glued it on with 3M Super Adhesive.  Not sure how long it will hold but magnets are easily replaceable if it flies off.

Hold please!!

Bottom Line:  It works!!  For a cheap unit, it does the trick.  Some functions include:  Speed, odometer, trip distance, max speed, average speed, run time, clock, ambient temperature, and stopwatch.  It's solar powered and has a back light too.  It's pretty easy to set up.  You just need to find your wheels circumference and punch it in.  If the speed readings are off, then adjust the circumference input.  I'm running 17" star rims with 2.25x17 IRCs.  I calculated about 1735mm circumference for this set up.  I verified my speeds with my Garmin GPS and its pretty dead on.  Some lessons learned with this unit is that the magnet sensor and magnet has to pass each other vertically at the "sweet spot" and be a maximum 5mm away according to the instructions.  At first, I wasn't getting any speed readings because they were too far from each other at 10mm away and not vertically aligned by about 2mm.  I think if you use a stronger magnet, you could increase the distance the magnet can be mounted away from the magnet sensor.  I also chose to mounted the magnet closest to the hub to minimize the centrifugal force that might cause the magnet to fly off.  I don't think this is overly important but its my engineer brain getting in the way again.  Overall, if you need to track gas mileage and speed "on da cheap", I would recommend this unit!!

Happy Tracking...