yeah seems like something up that could very well be iv never checked it against anything else.
with all the mix and match parts ive got im not realy sure about speedo either with 79 speed gear at wheel and 83 wheel and 130-70 tyre but ididnt mess with tach about the only thing i didnt mess with
i will say that when i modified the air box it sure started running good over a broad range of condition and im always mixing 2cycle oil,atf,diesil or something with the gas not all the time but a lot, things we did while farming all old oil got burned up in something never dumped you would think there would be down side but there isnt it realy all good and you sure got your money whorth out of the oil.
i guess someday ill try to see how corect things are on my gauges its hard for me to beleive im running this far off from everybody else