Fly 50 is a common scooter here in Finland. Usually for older people, when there is no rush. Piaggio Vespa 50 is premium, Fly is worth money with 30 % and above less priced. Comparing Kymco, less than Agility 50 and almost equal with Like 50 priced.
Heavy, so good to drive. 4T lazy, some say. When used normally with service, easily over 20 tkm/ ten years. No weak points with variator or electricity or whatsoever, that is what you asked.
2 valve motor is ok, 4 valve motors have had troubles with valves timing in some cases. Timing does not last.
I would go for 4T 2v Fly anytime. Reliable,quiet, low gasoline, enough big for driving 100 km or more in one time, and does the job easily. Also in wintertime, when serviced as manual says.
When sold here, version is restricted to 45 kmh moped.