How is a larger tire going to make a 6% correction on the speedometer, and only a 1% correction on the odometer?
My answer was directed to a particular post that was experiencing only about a 3.75% speedometer error, not 6%. He asked it a 70 series tire would help, and of course it would, since it has a larger circumference than the OEM tire.
Apparently the instrument panel logic board has two different algorithms, one for the speedometer and one for the odometer. If the algorithms were the same, it would be possible to ride your motorcycle at an indicated 60 mph for 10 minutes and have the odometer show exactly 10 miles, regardless of the speedometer error. Both indicated readings would still be incorrect, but at least they would agree. As it is now, they won't agree and I suspect they never will. That suggests two different algorithms, since there is only one electrical pulse.
Regarding the discrepancy between odometer and speedometer accuracy after the installation of a 70 series tires, the anecdotal evidence has been pretty clear: Speedo is spot on, odo is still slightly off. The percentage of error correction after the tire install is not linear between the two instruments. It is quite possible to correct a 3.75% speedometer error yet still have a 1% odometer error.
Those with speed-o-healers indicate that when the speedometer is corrected, the odometer is still off. One recent post indicated a true GPS distance of 254.9 miles and an odo mileage of 259.1 miles..showing a 1% error on the odometer of a motorcycle with a calibrated (within 0.1%) speedometer.