I've got a 89 that's been sitting around for a couple of years. I've got it running but not correctly. It will ideal but when you open it up 1/4 throttle it climbs in RPM and hangs there even with the throttle closed. You can get it to ideal again but you must use the clutch to load down the engine. I've checked the Diaframs and they are slidding up and down like they are sappossed to and the throttle works fine. Any one had this problem before. I've got a rebuild kit on the way.

slow return of idle = lean or you got a leak somewhere..

but someone else can confirm that..

I currently have the same problem. I have replaced air filter, checked vacuum hoses, removed the petcock, checked the Manifold boots, adjusted the mixture screws over and over, adjusted my floats, checked the all my cables, throttle/choke. I still cant get it fixed

I am now going to change the jets in my carbs and give that a go.

Its one of those problems that has a bunch of things that can cause it.
I hope my retting will take care of it

Someone mentioned in another thread recently to check the valve clearances as another possible cause.