The Yamaha Neo's uses an air-cooled motor with a horizontal cylinder. It is restricted by a washer in the variator and by the exhaust system. The washer can be removed, but the exhaust cannot be derestricted - it must be changed.
The dyno graph below shows the standard engine with and without the variator washer, and with a LeoVinci SP3 exhaust and the variator restricting washer removed. No other mods are carried out.

Further performance can be obtained by using a 70cc cylinder kit, a gear kit and a carb kit.