Speedometer Recalibration:

All vehicles come with speedometers that read faster than you are actually going. Since they can never be exact, they err on the side of speed readings in excess of actual. Two good reasons exist for this, the lawers are happy since no on can claim that their bike was going faster than they thought and that's why they got hurt, and because a slow bike can seem like a real fast bike if the display says so. These may be good reasons, but I want the truth.

Also, in addition to increaseing the error displayed on the speedometer, re-gearing is going to mess up the bikes speed data. The computer uses this information for a host of fuel and ignition calculations, so it is worth having right. Also, I am so anal about not getting poor data, that I could squeeze out diamonds. I had made a direct plug in connection for my Yellowbox speedo re calibrator for my F4i. It used the long standard 3P connector. Honda now uses the new sealed 3 pin connectors for their speed pulse senders. This time, I think that I will just splice the line. I need the job done now, and I do not have any of these connectors handy. Plan for this if you are going to do this job so that you do not have to cut your stock parts.

My speedometer was out by 1.9% with the stock 16/43 gearing as checked by WAAS GPS at a steady straight section of highway. This grew to 23.5% after changing to 15/47. This is a huge amount of error even with the stock configuration. On a stock bike the speedo would read 100 mph when you are actually doing 85.8 mph or 81.0 mph on a 15/47 regeared bike.

This is the formula that gives your speedometer correction factor given stock gearing:

You can figure out the actual speedometer error even if you have changed gearing and even predict correction factors in advance of the next gear change using the following formula. Note that if you tested the bike using stock gearing, the tested gears and the stock gears are the same numbers.

One additional part of this job that you may consider is jumping an auxiluary power line off of the pulse sender line. Since I had to bring the Yellowbox back to the glovebox anyway, I placed a two pin connector on the same line. My laptimer requires a 12 volt power supply, so this will be perfect. This is better than jumping off the battery since the line goes dead when power is off on the bike. Jumping off the battery requires an additional switch.

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