Here are the serial number sequences and some details as per the Honda Motorcycle Identification Guide 1958 - 1998, please note that the book is an American publication and there might be some minor diffrernces with the Australian models.
SL100 Motosport 100 (K0)
Sell date 1970
Frame No. SL100-100001~
Engine Number SL100E-100001~
Color; Candy Sapphire Blue, Candy Ruby Red, Candy Emerald Green
Fuel tank stripes & "100" side cover decal are white K0-K1, handlebars without cross brace K0-K1, frame is silver, headlight shell is unit color K0-K2
SL100K1 Motosport 100
Sell date 1971
Frame No. SL100-200001~
Engine Number SL100E-200001~
Color; Candy Ruby Red, Candy Emerald Green, Mars Orange
Fuel tank stripe is white, "SL100" side cover emblem is moulded plastic, seat shape is flatter, no rivets on side
SL100K2 Motosport 100
Sell date 1972
Frame No. SL100-1200001~
Engine Number SL100E-1200001~
Color; Candy Ruby Red, Tortoise Green Metalic
Fuel tank panel is yellow & "100" side cover decal is yellow, handlebars with cross brace K2-K3
SL100K3 Motosport 100
Sell date 1973
Frame No. SL100-1300001~
Engine Number SL100E-1300001~
Color; Candy Riviera Blue, Fire Red
"HONDA" fuel tank decal is white, "100" side cover decal is white, frame & headlight shell are black, rubber dust covers on control levers
The XL100 was introduced and superceded the SL100 in 1974, however you will find XL100 K0's with a model Identification plate stamped with a date for late 1973. My XL100 (K0) is stamped 10/73 which is it build date even though it is a 1974 model. The XL100 obviously all has frame and engine prefixies of XL100/XL100E.
CJ
