81' CB750

[Tyler.wise]

So this is my first time on a forum, and Im a newcomer to motorcycles. My 1981 Cb750 is my first bike.
Im having an issue , though, when I start the bike, the rpm go to around 3000, +-100. The idle screw is all the way out. I can't figure out how to get them to go down. When I rev it a little, the rpm will go up, and stick for a second before returning to 3000 rpm.. I'm not very mechanically inclined with motorcycles, so Id appreciate any advice.

[seestheday]

Could be a lot of things.  First thing that comes to mind is a vacuum leak (plus its really easy to test for).  Doing a search on this forum will tell you how to do the test.