Correct Dynamic Ignition Timing
After you've adjusted the valves (yes , I know you did it once , do it again) , you can time it dead bang by connecting a vacuum gauge to the manifold port below the carby and start it and warm it up , set the idle speed to 700 ~ 1,000
RPM and watch the gauge as you ever so slowly and carefully twist the dizzy ~ as the timing advances ,the gauge's needle will begin to rise ~ what you're looking for is the highest , steady vacuum reading . it can be anywhere from 15" to 21" but the important thing is to get the ' twitch ' out of the needle .
Now , you're good to go and can adjust the carby mixture screw and final idle RPM's down to 400 ~ 600 depending on your liking , it'll shift better the lower the idle speed is .
If you simply cannot get it to idle well until the vacuum is 15" or less , you have a vacuum leak somewheres .
I hope this helps .