OK . So you want to buy a scooter and you noticed it's from Vietnam . You read some negative articles from buyers who have had a bad experience and now your having second thoughts . That's good , you should have second thoughts but it doesn't mean all sellers from Vietnam are bad apples. VietNam has scooter shops on every corner . There are thousands of them in Saigon alone . What happens is that you get westerners who go from shop to shop and buy the cheapest bike they can find and then list it on Ebay. You also get Vietnamese Americans who return home and do the same thing . These are mostly people who have moved to Vietnam for various reasons and will do anything to make a buck.
I have been to Vietnam 6 times now . I have seen most of what is selling on the streets of SaiGon and can tell you if you buy from one of these itinerant dealers you will get burnt. There are however good dealers who do excellent work and have good guarantees . One gentleman is from Australia and he has an excellent reputation . He scooters are a little on the expensive side but absolutely straight up .He also has a very big parts business and sells to many Europeans.
There is another man who sells on Ebay who is Vietnamese. He and his family have been restoring scooters for 2 generations. His shop is near the airport in Tan Phu District . He uses only the best parts and has his own shop . I have been in his shop a number of times when parts arrive and have inspected them personally. They are top quality. His paint work is also the best I have seen anywhere . If you see his website you will know who I am talking about . You can buy good scooters from Vietnam , just take your time , ask questions and see if the seller has a reputable website . Good luck .
My rides : Vespa S150, Vespa VLB, Honda Cub 70 CC .. ride safe , wear a helmet and high visibility vest !