If it was working before you did the fork work it probaby is a something loose, electrical or vacuum seems most likely.I'd check all the fuses,it's possible there might be more than one fuse involved.
There are three switches that disable the cruise. Two are the front and rear brake switches which areokay ifthe brake lightswork, but the clutch switch operates a little differently.The brake switchesmake to disable the cruise, butthe clutch switch opensto turn the cruise off. I had an iffy clutch switch on my 86 SEI that was causing the cruise to drop out. It cured with a little WD-40.Clymers had some trouble shooting on the cruise controls on the LTD and SEI in the 84-87 book.
Follow theclutch switch cable tothe connector and make sure it's still connected, checkthat whole bunchof connectorson the left right behind the steering head under the top cover. I don't remember where the cruise control module was, but tracking the wiring from the actuator back ought to locate the module so you can check it's connections. Check the vacuum line to the actuator and it's source. A hand vacuum source and twelve volts applied to the actuator will tell if that is working. You could temporarily connect a volt meter to the actuator and then ride the bike to see if control voltage was being applied to the actuator vacuum valve if you thought the problem was with the actuator. Gotta get that thing working, once you have a cruise control on a bike it's habit forming!