Motorcycle Repair: piaggio zip 125 not going as fast as it should, piaggio zip 125, honda spree

Question
i saw that you mainly deal with mopeds under the age of 1990 but had no one else to ask about this.

i bought a piaggio zip 125cc scooter, which had not been used for around a year and was kept outside. When riding it around, i have found its top speed to only be around 45mph.  ive looked at other Ads with people advertising the same bike for sale, and when a top speed is quoted it is usually at 65-70mph.  Also i found an article by the independant on a piaggio zip 100, which is 25cc less than mine and believe is also a 4 stroke. They quoted a top speed of 52mph, "Driving around London meant I did not get to test its top speed of 52mph"

Do you know any reasons why a scooter would go slower than it perhaps should?

The scooter is a 2003 model with milage of around 6000miles. Whenever i get up to the top speed the engine changes sound, and has a kind of buzzing, tinkering, vibrating sound. Could there perhaps be a governer or restriction on the bike?

Thanks
Tim

Answer
Wow... I'm not real in depth on that brand yet, never worked on one sometimes depending on where you are there are restrictions. Rattling sounds at top speed is NOT normal. I have a 50 cc Honda Spree and a 63cc Yamaha Razz, and they both do around 40. I know my engine gets LOUD on those at top speed because mine are tuned even with a high performance CDI unit (so they'll spark stronger and will hit engine speeds of up to 10,000 RPM) and they still do not make those kind of noises. My guess, come to think of it, if you got a two cycle, may be piston rings. These don't last forever. I've replaced rings in my Spree 4 times now, and next time it is also getting a 63cc kit. My Spree has 10,500 miles on it.