Haha .... I used to do the same thing racing the pocketbikes 10 years ago by putting my then 8 year old son on it and letting him drag race against my friends, he would totally dominate since he weighed over 100lb less than everyone else... the guys didn't catch nonnative first why I was letting him do all the drag racing at first but it didn't take long before they figured it out and wanted me on the bike. He still dominated against most the other kids tho since he was still 20 lb or more lighter than most of them at the time. Now he's 19 and bigger than me but still quite a bit lighter. I'm sure he could get my bike over 43mph if the engine isn't maxing out its rpm on the street. Right now with the 44 tooth sprocket it feels like there's little or no load on the engine at 42 mph so there may not even be a difference.
if I was going for a speed record I would use as many aerodynamic nods as I could get away with for the class like those wheel discs to cover the spokes, the shortest bars I could still ride with, the thinnest wheels and tires, and knife edging the leading and trailing edges of al the frame and fork parts that face the wind, then finding a lightweight and slim rider to go for the record. Weight does factor in but aerodynamics will begin to factor in more and more is speed increases
