Small Engines (Lawn Mowers, etc.): Briggs Stratten, phase generator, small spring

Question
I have an 8hp B&S petrol motor running a 3.5 kva single phase generator. i cannot get the motor to run consistently. i have clean the carb out and checked and cleaned the jets. There is a small idler arm on top of the carb (this continually moves as the revs change)that I am told should have small spring on it to maintain some tension, but I am not sure this is correct. i need consistent revs in order to obtain consistent voltage. I have already burnt out an appliance from the engine over revving.  

Answer
 Hello Graham:

 Did you Soak the Carburetor Overnight in Carburetor Cleaning Solution? If Not, then the Carburetor can Still be the Problem. Sprays and Wires Will Not Clean a Dirty/Clogged Carburetor. Send me the Model, Type and Code Numbers Off of the Engine, Please. With these, I can Locate a Breakdown/IPL of the Engine and Better Assist you. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John