It seems the Kymco manual states, "Use unleaded gasoline with a research octane number of 91 or higher."
The Research Octane Number (RON) is not what we use in the US, we use the Anti-Knock Index (AKI). There is also the Motor Octane Number (MON), further confusing the issue.
http://en.wikipedia.org/wiki/Octane_rating In order to translate between RON (which the Kymco manual uses) and AKI (which US gas stations use), we have to do some math.
MON is a more stringent octane test than RON, so the MON will generally be 8-10 points lower than the MON.
So, we let this website do the calculations:
http://www.wolframalpha.com/entities/calculators/anti-knock_index/ra/6k/ue/ We know Kymco wants a RON of 91 or higher, so we plug that into the RON input on that page. We'll assume MON is 10 points lower than RON for this first run, so MON is 81.
The result is an AKI of 86. So, Kymco says with a RON of 91 and a MON of 81, we can run 87 AKI octane gas just fine (in other words, the 87 octane number as it shows at US gas pumps).
Let's do another calculation with the MON set 8 points lower than the RON.
That gives an AKI of 87. So again, we should be just fine running 87 octane gas in the scooter, according to the Kymco manual.
So, it would appear that running 87 octane (AKI) gas should be just fine for these scooters.