av7=american model. av10=european model.
Not to be nit-picking this but this bit if misinformation is enough. The av10 came around after Motobecane was bought out by Yamaha and transformed into MBK in the early 80's. Before that the av7 was THE motor that came on all the more recent motobecanes but MBK wanted to get into racing so they copied the design of the 103's motor and came up with the av10.
av10 builds are VERY expensive, if not the MOST expensive moped motor to kit. You are going to loose a significant amount of reliability by switching over to high performance racing parts. At the same time you are going to gain insane acceleration and a great top speed.