Need help with idle!

Vacuum leak for sure will do that as well as above posts , I use W-D 40 to find any vacuum leaks, start it up idle it down to say... 650 to 700 rpm and spray the side of your carb, ... then base plate ....and intake and if it raises in rpm you found one of many vacuum leaks. where do you have the trimming set at ? Oops for got to say block off your Vacuum advance and any port leaving your carb, remember your vacuum advance at the distributor could be leaking in the diaphram as well