Small Engines (Lawn Mowers, etc.): Sears blower, boat anchor, gas tank

Question
I was given  a Craftsman Blower #636-796911 ---37.7 cc taht hasen't run in abouy 6-7 yrs.
I drained the gas tank and refilled it with 20-1 mix, Replaced the plug with a new L82C . and removed the carb and sprayed thoroughly with carb cleaner and replaced the air filter. It starts ok and runs for about 15-30 secs but I have to keep playing with the choke and throttle. I've never taken a carb apart so am hesitant to attempt it.
Any ideas?
Thanks very much.

Answer
eric

The mix  needs to be 50-1 not 20-1 what is happening the engine is burning to hot and wont stay running eventually you will burn out the rings & pistons causing it to used a a boat anchor.Also the carb diaphragms are probably dried out & rotted,cracked & not flexible anymore.