Wow, someone smoked the piston? Good grief. They must have been running it without oil or something.
Make sure that they checked that the oil pump is working before you take it out on a trip. On a kymco there is an oil pump that meters the oil into the air/gas mixture right before the reed valve. Also, you probably already know this, but make sure that when they changed the top end, they adjusted the carburetor air/fuel ratio.
Once you remove the variator boss limiter and modify the ECU to disable the speed limiter, an otherwise stock Kymco 2-stroke can reach 45mph+. 30mph is the "as shipped" configuration, in which the variator boss prevents the variator from closing all the way (and reaching the highest ratio), and limits the engine at 6000RPM. There is no way to trash the engine in this configuration unless you run it without 2-stroke oil or screw around with the carburetor jetting / needle settings and make it run lean. The stock exhaust is also going to make your power start to drop off once you're at 8000 rpm.
I weigh 260# and my Cobra Racer 2T will pull me up to 50mph (GPS verified) on a flat run, using a Technigas pipe, lighter roller weights, and carburetor adjustments so the engine doesn't burn up (the bike is otherwise stock). It can go a little faster downhill (55mph), but I'm nervous about that since its already at 9500rpm when I'm doing 50. I'm betting that the 72cc will allow you to get up to speed faster, but didn't add much to the top speed. Unfortunately my setup produces its best power at 8200+ RPM and runs pretty rich below that (needed due to how much air goes through when you reach resonation), making it "not the most fuel efficient 49cc scooter". 40mpg, lol. My Xciting 250CC (which is a heavier bike @ 400lbs, not that the Cobra is light @ 240 lbs) accelerates about the same for the first 40mph, but has a top end of 85ish MPH and gets better mileage to boot. I kind of needed that oomph, despite the fuel efficiency hit, because of how heavy I am (and my home town is somewhat hilly).
For comparison, the YY250T doesn't want to get above 6500RPM @ 70mph on the highway (getting the same mileage as the XC250), and that's WoT, no oomph left. (I know its not rev limited since I can get it over 8000rpm on the center stand.) It's not a suitable vehicle for travelling on the highways in Connecticut (whereas the Xciting 250 is just barely suitable), since we have left-hand exits and people are usually doing 80 or more in that lane, making crossing over a risk I absolutely don't want to take on the YY250T.