Sears ST 16,Carb.??

[Joe 427]

My tractor 16 hp one cylinder will idle for 5-10 seconds then start to die out then the throtle will open to wide open then start to idle fine ,then it will do it all over again

 

[joe csuti]

The most common cause of this series eng to surge/hunt for it's speed is plugged/restricted idle passages in carb body due to dirt/gum,you can try opening idle needle 1/4-1/2 turn,if that doesn't cure problem,remove/dissasemble carb,remove any brass plugs/welch plugs in body,soak in carb cleaner overnite & run a fine wire thru all passages you can find then blow out passages with compressed air,buy/order a rebuild kit from sears/local dealer & rebuild carb or see if you can find a new oem/aftermarket carb on ebay/online dealers.

 

[MNGB]

Another thing to check is the throttle shaft for wear a very common thing on the Walbro LM series carbs. As Joe post there are carbs for that engine listed on e bay pretty regular also theirs a fellowing Ga that will sell you parts or will rebuilt the carb for you.
http://www.carbrescue.com/intro.html