Hi DrSwammelstam,
Well, it appears we're in the same boat! I've had the exact same scooter for about 3 months and am having all the issues you report. Piss poor acceleration as standard, but maybe not quite as slow as yours. Currently the speedo just nudges 50kph going downhill and hovers round 44-45kph on flats. On steeper uphillls, it can drop to around 40kph which is annoying the hell out of me.
Weird thing is, it went faster in the first couple of weeks I had it. I'd get about 53kph going downhill, but then it lost loads of speed just before the first "tightening up" service at 500km (wouldn't even hit 45kph). After that it ran better, but I never got that 53kph top speed again. Maybe it's because I put on weight over the summer!
I weigh about 82kg now, so maybe that has some sort of negative effect.
(As an aside, my old moped was a SYM Fiddle 50 II and that did 45kph uphill, downhill and on flats! So I guess the comparative average speed is the same LOL!)
Anyway, my KYMCO manual has no technical drawings, so I removed the seat and had a poke around. My first thought was to swop out the CDI, but I couldn't find one.
Don't ALL mopeds have one to govern the speed?? I then tried to take the panel off in the footwell, but couldn't. I'm guessing there's nothing under there other than the fuel tank, but could be wrong. I'm not really technically savvy enough to do anything else like mess about with rollers and stuff, so I guess if there isn't a CDI I'll have to ask the mechanic at the next service if he can get some more juice out of it some other way…
Let me know if you have any luck with getting yours to run faster.
/Gwhizz