ON THIS AFTERMARKET COIL THE BLUE WIRE REPLACES THE GREEN WIRE ON THE CT90'S THIS WORKS FOR THE IGN COIL ON ALL CT90'S K0 THRU 1979. "IF YOU HAVE A CL90 OR CL70 THIS WILL WORK, IT IS JUST THAT THE BOLT PATTERN MAY BE OFF" here is the scoop on the st90's fitment (thanks!! Dean) Jack, This coil is a fit on the ST90! Bolt holes match and the TEC# is the same as the original. The one difference is the leads. On my old one the green has a female connecter and the new one has a male> Not a big deal! Thanks, Dean S90 OWNERS, THIS WILL WORK ON THE S90, NOT SURE ON THE PRIMARY WIRE TERMINALS , LOOK AT WHAT YOU HAVE NOW AND BE PREPARED 87A