JetPilot wrote:That is crazy, very different from my results, but I do not have your types of bikes. Are they older bikes ?
The most recent Wing was a 2003. The earlier Wing was an '83 Aspencade, but I wasn't quite as compulsive about data collection back in those days. The Viffer was a '93 model in pearl white instead of the usual Very Frickin' Red. By the time a tree hit it in late '02, it had a full set of Givi bags of various sizes, a Givi screen, a Corbin saddle (which I will never do again), Helibar handlebar risers, and several other mods that let me know that I was craving a touring bike again. So when the tree totaled it, I replaced it with the '03 Wing. It was with the VFR that I started keeping the same sort of compulsive records that I always had done with the cages.
Before that, my only other 750 was the 10th anniversary edition CB750K LTD ('79 model) which I rode at the end of the 80's, beginning of the 90's, after the '83 Aspencade. Also, way back in the day, were the earlier Silverwing (GL500I, basically a factory-dressed CX500 transverse twin) and another scooter back in the 80s, an Elite 120.
At some point, with some arm twisting, I might be compelled to tell stories about traction, speedometer & odometer readings, tire life, and the '03 Wing (my favorite bike to date; if way oversized for the way I'm riding these days). For now, just know that it is on the last three bikes ('93 VFR, '03 GL1800, '14 Forza 300 (bought in '15)) that I have kept records of every penny spent, of every mile ridden. And on two out of three of those bikes ('97-present) I have found that Honda speedometers are optimistic, and that the odometer ticks over too quickly. Your bikes may have different engineering.
JetPilot wrote:The radar signs are not always so accurate, GPS is always dead on accurate, and is the best way to compare.
I accept that the radar signs are "not always so accurate," but I find that they are always identical in what they read -v- what my gauges say. Whether it's one of the permanent installations (1 mile north of me, riding through a college shopping/drinking area; 0.8 miles east of me in a school zone) or one of those temporary trailers that show up (on my route to church or my route to work), they are all calibrated the same and show exactly the same reading WRT my dashboards. I expect that they are calibrated the same as the equipment inside local LEOs vehicles, so I try to make sure I know what their equipment is likely to say when I go past them.
OTOH, my experience with civilian GPS is varied. In areas with marked elevation changes (including rough seas and mountain roads), the instantaneous velocity reading varies wildly. Even when tracking a walk for health data, the momentary velocity can vary in ways that make the head spin. I have seen much more accurate reading from specialized GPS systems, both military and WHO based, but those have only let me know that the tech is available, but not to plebeians like my own self.
For the best ODO corrections available to me, highway mile markers on a long trip, I know that my Honda gauges are optimistic at best.
And if my own mpg calculations were in error because of variations in how I filled my tank, I would expect that some of my spreadsheet readings would be higher and some lower than what the gauge on the dash reads. But so far, every single gauge reading except one has been higher than what my trip meter and the gas station's gallon reading told me; for that one, I think that the gas station's meter was off. It told me that I had only topped up with enough fuel to make almost 110 mpg on that tank, but the next three tanks have all been within normal parameters. I'm pretty sure that I got free gas on that visit.
I'll attach a screenshot of the relevant bit of the spreadsheet:

- Screen Shot 2016-12-23 at 4.16.39 PM.png (164.24 KiB) Viewed 1412 times
So, all-in-all, I'm willing to say that my instantaneous mpg meter is optimistic, although my speedo is much more like what the local LEOs see than my previous Hondas have been.
As always, YMMV.
Pax et bonum,
Michael
wishing everyone a Merry Christmas and Happy New Year