This video covers the 100cc rotary valve two-stroke engines that Parilla (IAME) homologated from 1980, the year they won the Karting World Championship with Peter De Bruijn, through the TT38 and TT39 homologated in 1998 for use in 1998, 1999, and 2000. It compares how the engines evolved in that span, including cooling, bore and stroke changes, how the rotary valve changed, and power differences between the first of these engines and the last. Models listed are TT27 in 1980, TT31 in 1983, TT36 in 1989 and 1992, TT37 in 1995, and TT38/9 in 1998.