Biknut, have you even built a 4-stroke motorized bicycle yet? You're talking crazy over there, saying a chinagirl is just as reliable as a 4-stroke.
I spent 4 years with 66cc chinagirls. I've spent 18 months with my 49cc Huasheng. From my experience, a chinagirl needs more work in one month than a Huasheng in one year. In fact, all I've had to do to my Huasheng in 18 months is a valve adjustment and 4 oil changes. I haven't had to adjust anything else on the engine. I haven't even had to tighten a loose bolt on the bike. Even with the bugs I had with my shifter 4G in the beginning, it was much less work overall than any single chinagirl I've had, and I've had 5 of em. Also, when you get a Huasheng (or any 4-stroke), you already know it's not going to need any work to make it reliable
You want to look at cost, you aren't taking into account running costs, either. A 49cc 4-stroke uses >25% less fuel and arguably less oil than any chinagirl, mile for mile. A chinagirl costs more in a year than a Huasheng just to get around, and we aren't talking "spare parts" yet.
Commie copy of a 1930's commie engine vs a commie copy of a modern Japanese industrial engine. Technology wins again.