Both my CT70K! and Z50J1 don't spring back that well. It can come in handy though if it's not idling well.
Here is the model guide. e.g. my K1 was built in December '71 so it's a very early K1
Year ID Colors Serial Numbers Engine / Trans
1969 KO Candy Ruby Red, Candy Gold, and Candy Sapphire CT70-100001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1970 KO Candy Ruby Red, Candy Gold, and Candy Sapphire CT70-100001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1970 CT70H HKO Candy Blue Green, Candy Emerald Green, and Candy Topaz Orange CT70H-100001 4 Speed Manual Clutch,72cc Overhead Cam Engine
1971 KO Candy Ruby Red, Candy Gold, and Candy Sapphire CT70-100001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1971 CT70H HKO Candy Blue Green, Candy Emerald Green, and Candy Topaz Orange CT70H-100001 4 Speed Manual Clutch,72cc Overhead Cam Engine
1972 K1 Candy Ruby Red and Candy Yellow Special CT70-2000001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1972 CT70H HK1 Candy Ruby Red and Candy Yellow Special CT70H-2000001 4 Speed Manual Clutch,72cc Overhead Cam Engine
1973 K2 Candy Topaz Orange and Candy Riviera Blue CT70-2100001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1974 K3 Candy Topaz Orange and Candy Riviera Blue CT70-2300001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1975 K4 Mighty Green CT70-2400001. 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1976 Tahitian Red CT70-2500004. 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1977 Shiny Orange CT70-2600008 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1978 Black CT70-2700005 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1979 Bright Yellow CT70-5000001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1980 Tahitian Red CT70-5100001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1981 Tahitian Red JH2DD0101BS200002 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1982 Tahitian Red JH2DD0101BS200002 3 Speed Auto Clutch, 72cc Overhead Cam Engine. Last year CT70 in US till 1991.
1991 Tahitian Red JH2DB010MS000001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1992 Tahitian Red JH2DB010NK100001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1993 Tahitian Red JH2DB011PK200001 or JH2DB010PK200001 3 Speed Auto Clutch, 72cc Overhead Cam Engine
1994 Tahitian Red JH2DB011RK300001 or JH2DB010RK300001 Last year of the CT70 in US.