I get that question all the time and I don't know how to answer it. Our race distance is 150 Ft. on pavement. We use a flagman so we don't have any time slips. I did carry a GPS unit one day and got a top speed of 32 mph. That was with flathead briggs......I have an OHV in it now. I have only raced it one time with the new engine, but it feels good!!!
I don't have a clue how fast it would go if I just topped it out. I don't street race, I have no desire to take that risk, and I don't want to blow up or wreck my mower doing something that is frankly......silly.