Hi darwin,
You might be right about scales being wrong, and I am sure my speedometer on my prototype is very, very liberal.
However we managed to add over 6 MPH by tuning the exhaust, adding adjustable main jet, and finding the best drive ratios. The bikes tested we used on the street and all were able to start from a stop without pedal assistance.
We also discovered why the HS was faster on top end than the Honda. The HS has a much larger main jet, and if the HS carburetor is used on the Honda it will match the HS top end speed.
I use dynos & Roller Roads [owned by others] to compare the changes, not as an exact science for accurate speeds. It is next to impossible to find two identical dynos, so it makes good sense to test changes on the same test equipment whenever possible.
By using the same test equipment [owned by others] I was able to set the speed record on a Whizzer @ 68 MPH in 2005. The Whizzer started out at 31 MPH and ended up above 70 MPH on the last test.
Until now I have resisted doing a little magic to the little 4 stroke, but I can no longer fight off the urge. Looks like I might have my "brand X" 49 CC 4 stroke pulling wheelies and setting new records not to far into the future.
Here are a few photos of the the record setting Whizzers and the "brand X" [40 MPH] 49 CC 4 stroke.
Have fun,