Do you own this model bike? At 60 mph on flat road without tail wind I bet it can’t do 43.4 mpg. Maybe a 600 CC or smaller bike.
I don’t know. But last summer I drove a Yukon on a church mission trip for a week. On the return trip the mileage monitor said that we were getting 20 mpg. That included my sitting at a Dairy Queen and reading with the motor running for a good half hour before going on down the road. If the guage wasn’t lying to me, why would GM be paying for advertising about the new hybrid Yukon that gets 20 mpg on the highway?
The only thing that can be legally modified is the pinion factor to account for changes in axle ratio and/or tire size. However, to change this to make a customer think they are getting better fuel economy would be fraud if the customer isn’t told, and just dumb if the customer requests it. The change would indicate more miles on the odometer than the car really traveled.