"Yellow Box"

[Shaman]

I'm planning on adding two teeth to the rear sprocket of my bike this year for a little bit more down low power, as I don't really need a 300km/h top speed.  Except perhaps at Mosport.

What I'm concerned about is "Yellow boxing" my bike, which is apparently a box that plugs into the wiring harness and does speedometer re-calibration.  I need this, since the stock speedo is off by about 10% or more and it would be nice to know my actual velocity.

Any comments?

[wes-ninja250]

What's the big deal? I never look at my speedo, anyhow. And 10% is an easy number for math purposes, since most of us ten fingers.

As long as the box ONLY intercepts the wires on the way to the speedo, it won't affect the bike.

The speedometer is a probably basically just a pulse-width modulation solenoid/motor. All the yellow box would do in this case is change the width of the pulses. If you were so inclined, you could probably build one yourself out a BASIC Stamp-2 microcontroller or something similar. Actually, you might even be able to cobble together a clever R/C, op-amp design to do this for under $20 in parts. (Note: I would not be so inclined).

Wes

[Shaman]

What's the big deal? I never look at my speedo, anyhow. And 10% is an easy number for math purposes, since most of us ten fingers.

I try to keep it at under 50 over.  Without looking, I'd easily be over the point of no return.  Not that I don't ever break my rule. 

The speedometer is a probably basically just a pulse-width modulation solenoid/motor. All the yellow box would do in this case is change the width of the pulses. If you were so inclined, you could probably build one yourself out a BASIC Stamp-2 microcontroller or something similar. Actually, you might even be able to cobble together a clever R/C, op-amp design to do this for under $20 in parts. (Note: I would not be so inclined).

Yellow boxes are probably $60.   Not a savings worth attempting, I think.  Part of the issue is, as I understand it, one can adjust the yellow box on the fly.

[wes-ninja250]

> Part of the issue is, as I understand it, one can adjust the yellow box on the fly.

You pretty much have to be able to do this, in order to make it accurate. Tire size, tire wear, and gearing will all affect the speedo reading (assuming you have an RPM + gear driven speedo.. mine reads the front wheel so gearing changes don't matter).

The easiest way to calibrate one of these is with a "measured mile", a lap timer, and a calculator. If you're doing it on new tires, leave it about 1% high. Highway 416 just north of Brockville has really well marked "mile markers".  You want to make sure that you're using a road length of at least 10km for good accuracy.. And ride a STEADY pace (say, shoot for exactly 110 kph indicated), trying not to change lanes. So early in the morning is best.

BTW, $60 is a good deal, I wouldn't think twice about trying to build one if it could save me anything less than $150.

Wes