On a '98, you can remove the slotted cover on the LH side of the bike and use a ratchet/socket to rotate the assy. No disconnecting of the actuator required.
Then, as jag says, look into the exhuast port (pipe off) to see the main valve and the subports move as the should and return as the should. The main valve will raise on activation, the subports will rotate in sync to open on activation. The whole thing should return to 'at rest' by itself when you release pressure on the nut.
Note there is a detent ball underneath the rod right at the nut on the LH side. If it's clean and working, you'll hear a 'snick' when you first turn the nut, and hopefully a like 'snick' when the main spring (on the clutch side of the motor) returns the KIPS back to its static state.
Check the suspension, too. It takes consistent maintenance to keep the unitrack/swingarm bearings in good shape.