I have a Seca 750 1982. Once bike gets up to temp the idle stays high. When you let off the gas and pull the clutch in the RPMs stay high. this will drop back down if you let the clutch back out or work the throttle. If you turn the idle screw down the bike will idle to low. Any help?
If turning the idle screw down causes the bike to idle too low, and turning it back up causes it to idle too high, then I’d bet you just need a simple tune up.
When was the last time you adjusted your valves?
I bet it’s been a while since you synced your carburetors too!
Doing those two things I’m almost positive will solve your problem (assuming the bike is running good otherwise).
It’s also possible you have a clogged pilot jet or two. Have you had the carbs opened up for a cleaning in a while? When it’s idling too low is it firing on all 4 cylinders or just 3?