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When You're Tired Of Doing The Math
Make Your Digital Speedometer Accurate (finally)
Gadget
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Those of you with analog speedometers don't need to read this, it won't do you any good and you'll just want to gloat anyway because your speedo's are pretty darned accurate already. Gloating is bad for you.
Those of you with the digital gauge package that comes with the Fuel Injection on Vulcan Classics, Nomads and Drifters
(except 2000 Nomad) are painfully aware your speed readings are way off. How far off? Try ten percent! That not
only means the speed reading is inaccurate but you're piling up 10% more miles in that little odometer window than
you're actually traveling. That's 10 extra miles every hundred, 100 extra miles every thousand...shoot, that's
a thousand extra miles showing on the bike every ten thousand indicated! Now we're talking serious error that's
going to cost you money!
You may be thinking Kawasaki could (should) have gotten this right in the first place but the optimistic speedo seems to be a character flaw with almost all metric motorcycles, especially those made in the orient. Vulcans read high, sportbikes read high even the luxo Goldwing has a healthy error built in. Don't go screaming to your dealer demanding accuracy, the Federal Government (yours) allows up to a 15% error, plus or minus when it comes to speed readings.
Now there is a wonderful fix (two of them actually) if, like I was, you're tired of constantly doing the math. "I want to do 70 so I have to run the speed reading up to 77", or "I'm in a 40 mph zone which means I can really do an indicated 44".
The "Yellow Box" ($100) from Black Robotics and "Speedo Healer" ($84.99) from SpeedoHealer.Com (or the U.S. Distributor) very efficiently recalibrate the signal being sent from the speed sensor to the instrument. How do they work? You can check the websites for details about algorithms and such. The bottom line is..it works and both are very simple to install, one a bit more so than the other.
There are differences between the two products the main one being the way they attach to your bike.
Yellow Box requires some very minor wire cutting (see instructions below) while SpeedoHealer simply plugs in.
The methods of calibration are very different between the two. With Yellow Box each dip switch (see photo
above) recalibrates in fractions or groups of percentages. I.E. one switch is the equivalent of 1 percent
while others could be two, three, five etc. You turn switches on/off to get the total you're looking for.
SpeedoHealer uses a combination of switches and a press of the button on the unit to set a flash memory. There is a calculator on the website that generates personalized instructions for this making it all extremely simple. Oh, that button? It is also a top speed indicator. When pressed (with the bike stopped) it will show your highest speed since the last reset right on your speedometer. (shhh, don't tell the cops)
Below is the installation guide based on the slightly more involved Yellow Box install. If you choose
SpeedoHealer use the same basic instructions (including testing each wire for signal and voltage) but use the simple
'plug-n-ride' cable 
instead.
Tools You'll Need for both units unless otherwise noted
10 mm socket or wrench to remove both shift pedals
14 mm socket or wrench to remove left floorboard
5 mm Allen wrench to remove the left side engine cover (4 bolts)
Circlip remover or small screwdriver to remove left floorboard circlips
Wire cutter and/or stripper (yellow box only)
Multimeter or 12v test light
Soldering iron (yellow box only)
Electrical Tape (yellow box only)
Tools that help
Whiteout (or marker) to mark position of shift levers so you don't have to play with them when re-installing
Electric Drill if you put the box where I installed mine
Here's How (thumbnails are provided for the bandwidth challenged. Click on them for
larger photos)
It will help a little if you have a lift for your bike. It certainly isn't necessary, but allows you to sit comfortably on something besides the garage floor while working.
1. Remove the left floorboard. You'll need a 14 mm socket and possibly a breaker bar if the bolts are at all rusty. If the bike is on a lift just loosen the front bolt just a single turn and remove the rear bolt. The floorboard will spin down out of your way. If your bike is on the sidestand it might be simpler to completely remove both bolts and the entire floorboard bracket.
2. Remove both shift levers. You might want to mark the lever positions to make re-assembly simpler
3. Remove the left side cover (four 5 mm cap screws)
4. Locate the speed sensor (finger is pointing to it in this photo) 
Note the wires exiting the
actual sensor are brown but after the connector they are black or light green. The latter are the wires I'll be
referring to through this instruction. The photo shows the three wires already unwrapped from their electrical
tape and separated, ready to cut or splice for Yellow Box. Note the unplugged connector (just below the separated
wires where the red SpeedoHealer cable will simply be plugged in, no cutting necessary.
| Black w yellow stripe=ground | Light green w red stripe=speed signal | Light green w black stripe=12v positive |
5. You will only be cutting (for Yellow Box) a single wire. It is the light green with red stripe wire that sends the speed signal from the sensor to the instrument. You can (should) just peel back the insulation on the black wire and the light green with black stripe wire. Note you can use those clamshell clamps to make your splices but they are never recommended on motorcycles. They vibrate and have been known to actually cut wires eventually. Don't actually attach any wires yet
6. It's time to figure out where you'll be stashing the box. As it happens (even on California models) there is
plenty of room under the left cover. 
Note mine is a California bike so has the charcoal canister under the cover and
that's what you see behind the yellow box. I drilled a 3/8" hole through the backplate and ran the computer
wiring harness out through that hole. Don't worry about sealing it up just yet, we'll do that later.
7. Now you can measure the length you'll need for the harness wires if you're using the Yellow Box. Allow a little extra 'just in case'. Cut off the excess wire and save it someplace for a day you need a foot of wire for another project. There is plenty of harness available in the SpeedoHealer package and cutting is not recommended.
8. (For Yellow Box only---If you're installing SpeedoHealer skip to #10)
It's time to solder (or clamp if you really must but it isn't recommended) Please refer to the instructions
that come with the Yellow Box. The following is the color code at this writing
but you never know when a manufacturer will change harness colors so don't consider this any sort of gospel. "at
this writing" you will solder (or attach) the RED wire from the Yellow Box to your previously identified
12 volt power wire (light green w black stripe). Per the earlier instructions you have not cut this wire but only
stripped back a bit of insulation so you can solder the Yellow Box wire to it. Now do the same with the
BLACK wire from the Yellow Box, attaching it to the previously identified ground wire (black w yellow stripe).
Once those are soldered it's time to cut the signal wire. Deep breath and.....snip! The instructions will tell
you to remove 3/4 of an inch of this wire for a nice smooth harness when you're finished. For this application,
forget it. There just isn't wire to spare. Solder the WHITE wire from the Yellow Box to the sensor side
of the signal wire. Solder the GREEN wire from the Yellow Box to the speedometer side of the signal wire.
Don't tidy things up just yet. It's time for a test!
9. Per the instructions that come with the Yellow Box set the dip switches 
to the following settings:
(1 is on, 0 is off) 0 1 1 1 1 1 0 0 turn on the ignition and turn your rear wheel. This is easy if it's on a lift,
you can walk the bike back and forth a bit if it's on the ground. The red light will blink as the sensor sends
its signal. The faster you move the faster the blink. If that's happening you're golden on the input connection.
Turn the ignition off.
Now set the dip switches to 0 1 1 1 1 1 0 1 . Turn on the ignition and look at your speedometer. It will be reading just shy of 10 miles per hour. The Yellow Box is sending a steady signal to the instrument. If you can wiggle the wiring and there is no fluctuation in the speedometer needle your output wiring is terrific. Turn off the key.
10. Tidy up your wiring by wrapping everything in electrical tape. If you're an over the top neatnick like
someone I know you can slide some 1" plastic wire sheathing over the top of everything and give the entire
harness a finished look. 
11. With everything back together you're going to forget the Yellow Box or Speedo Healer is
even mounted on the bike. 
It'll take awhile to stop doing the math though.
12. It's calibration time. If you have a GPS or know someone who does this is a piece o' the proverbial cake. If
not then you have a little math to do. With a GPS go for a ride (faster is better in this case) and
note the speedometers indicated speed versus the speed your GPS is showing. If you don't have
a GPS available you can use highway mileage markers or a trusted friend in a car (with a known accurate speedometer)
sending speed signals by hand or talking to you on a radio. Let me make it simple for you. The
number is going to be 10 percent or extremely close. I.E. at a true 60 mph your speedometer will show
66 mph, at 70 your speedo will show 77 etc.
13. (Yellow Box only, if you used SpeedoHealer go to #14)
The Yellow Box instructions are extremely easy to understand. Set the dip switches ( 0 0 1 0
1 0 0 0 ) If your bike is off by the same amount as mine this figure will give you a 1 mph error at 25 mph (speedo
reads 24 at a true 25) but by the time you reach 40 the speedo and GPS are right together up to 85 (the highest
I've tried it so far).
14. (SpeedoHealer Only, if you installed Yellow Box go to #15)
Trying to explain the calibration method for this unit here is nearly impossible. Basically you use two of
the dip switches and combinations of button presses to re-flash the unit memory. There is an online
calculator here that will compute your
correction percentage and then will produce printable instructions for calibration. Just click on the
"on-line calculator" button. It's really simple, just too cumbersome to put in written instructions
(which is probably why the calculator/calibration method isn't included in the SpeedoHealer package.
Before calibrating put the unit through its self test as detailed in the included instruction sheet and also on
the company website.
15. When your new computer is calibrated and you're pretty sure you won't be fiddling with it anymore, grab a hot glue gun or tube of Silicone glue and seal up the hole you drilled for the wire to pass through the side cover back plate. To help keep dirt out of the switches you can use either of those things to seal the switches too. Just lay a bead right over the top of the dip switches (both peel off if you need to make changes later). Put the side cover back on, go for a ride.
Thanks much to the manufacturers of these devices for creating a product that, once and for all, through tire size
changes, (sprocket changes for bikes that can) and even changes from bike to bike (you can take both with you to
your next bike) those who own one never again have to wonder "how fast am I 'really' going?".
