No stock 50cc scooter is going to go 50 mph. Not even close. I have modified 50cc pedal mopeds (Puch, Tomos) to do 50 mph, but they had very short lifespans. If you see a 50cc scooter doing 50 mph, it has been SERIOUSLY modified.
Also many states are now passing laws about where you can ride a 50cc unplated scooter. 35 years ago I put over 20,000 miles on a stock Puch MaxiSport, at 30 mph, on non interstate roads. I toured 4 states, and a good part on northern Mexico. I wouldn't even consider doing it now. The speed limit was 55 mph back then. No people drive 80 mph on 65 mph roads around here. You will need at least a 125cc scooter to ride where you want to safely and legally. I recommend either a Yamaha Zuma 125, or a Genuine Buddy 125. These are both top notch scooters. I'm getting ready to buy a Zuma 125 in a few days. I would consider a Buddy for sure, but the Genuine dealer does not take trade ins.
I won't spend more on a bike than I think it's worth, but if it's a good deal, I don't seem to have a problem buying bikes I don't need.
2002 Vulcan 750, 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
1980 Puch moped