Idle too high

Hi!

I just finished changing the head gasket on 1981 Suzuki GS850G. The bike
fired up nicely, but idles too high, around 3000rpm. I tried adjusting the
idle screw, but it didn't help too much. I checked to see if the throttle
and idle cable are stuck, but they are loose.
Any ideas what can it be?

Thanks,
Dejan