Small Engines (Lawn Mowers, etc.): 18hp briggs, carburetor body, briggs stratton

Question
18HP Briggs & Stratton (in a Troy Bilt) loses power under load and runs hot.
Model- 31D777   Type- 0233E1
This engine has had the head replaced on it last year, thinking that it had a burnt valve after it sheared the key.  It seemed to run fine after the head and key were replaced. I noticed that at the end of last summer it seemed to be running hot, the pipe and muffler glow red  after a few minutes of running. I replaced the muffler at the beginning of this year because the old one was burnt out. It has now burnt the new one out.
The first mowing this year it started running rough, no power when under a load and backfiring. It had once again sheared the key. I replaced the key and now it idles and goes through the power band OK from what I can tell but it doesn’t have good power when I turn the blades on. With the blades off it sounds and runs fine but still gets hot. If you go though a little taller grass it falls on it’s face and you have to sit there and let it build power. Or if you are going up a grade it struggles to get up it.
I have taken the carb off and cleaned it although it appeared to be OK. The plug has a gray/white look (running lean) at the electrode but has black dust at the base (like it’s running rich). I’m lost on this and need help. Needless to say I don’t think that the head was the problem last year.  ???


Answer
Doug


Did you Soak the Carburetor or Manually Clean the Carburetor. A Small Engine Carburetor MUST BE SOAKED to be Properly Cleaned.  Remove, Disassemble and Soak the Carburetor Overnight in Carburetor Cleaner (I Use Gunk). I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning. You Only have to Remove the Bowl, Float Pin, Float (if Applicable)  and Needle Valve and Any Adjustment Screws that Go Into the Carburetor Body. The Welch Plugs Do Not have to be Removed. Then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts. Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidental Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required. If this Carburetor has Air Mixture Screws; Are they Correctly Set?  ****Turn the Idle Air and Main Air Mixture Screws In Until SNUG **Do Not Jam** Then Reverse Both Screws 1 1/2 Turns. Holding the Throttle Full Open, Start the Engine. Turn the Main Air Mixture Screw Clockwise Until Proper Revs are Obtained. Occasionally you May have to Turn this Counter Clockwise to Achieve the Proper Revs. Now Allow the Engine to Idle. Set the Engine Idle Screw (Not Idle Air) so the Engine will Stay Running if Required. Now Set the Idle Air Mixture Screw so there is No Hesitation when Throttling from Idle to Full Throttle. Reset the Engine Idle if Required.**** Send me the Model and Type or Spec Numbers Off the Engine, Please. They are Usually Stamped Into the Blower Housing (metal engine cover) Above the Spark Plug or Muffler. With these I can Locate the Proper Manual and Better Assist you.