We purchased 2 of these around June 2007. They have just been used constantly over the past 7 days (October)  in Hill End NSW. (A land of steep slopes, Shale, Quartz and at the moment - extreme dust)
Construction of both bikes was about half an hour. The 90cc model went together easily. The 110 was a little more difficult where the tyres were concerned. (16x8" Tubeless) The home compressor fixed this problem, along with me standing on the tires to blow out the beadings.
BOTH bikes were unsupported with split pins in the suspension, steering and ball joints. This was fixed for about $5 at the spare parts shop.
During the week the we experienced the following problems:
90CC - Two flat tyres, plugged externally with a tubeless repair kit. Starting at cold was reasonably easy, and once done, the bike restarted reliably on each attempt. No other problems.
110CC - One flat tyre  - fixed as above.  Very difficult to start from cold, required jump starting from a cheap car battery that we had taken with us and a short battle with the choke.  The standard battery  if anything is short of power requirements. Looking at a size increase to address this.
Both bikes returned home very dirty. I note that they will need a couple of rubber bushes replaced - but that's about all.
Both bikes were made in China - and considering the small amount of money that was paid for them, they performed brilliantly. The kids and us all had a great time with them. I should add that they both coped with 100KG loadings, without any stress or handling problems.
Now - to find some tyres that are greater than 2 ply................