Small Engines (Lawn Mowers, etc.): Throttle free engine runs to slow, briggs and stratton, mulching blade

Question
QUESTION: I have a Murray 22" 5.57hp Quantum lawn mower.  It has the throttle free design so it controls its own speed.  It is running at what sounds like a high idol but should run faster.  It has a mulching blade and cut the grass uneven.  It does not cut well on the left side as you stand behind it.  I think this is caused by to slow an rpm.  I can manually open up the gas to run faster but there is no tension to pull it that hard.  Where is the governor and its spring?  If the spring is attached is there away to adjust it?
ANSWER: Hello Steve:

If the Mower is Cutting Uneven. Check for a Bent Crankshaft. A Bent Crankshaft will Cause Uneven Cut and Effect the Engine Operation as you Described. Remove the Spark Plug. Tilt the Mower so the Spark Plug Hole is Pointing Up. Turn the Engine and Watch the Blade Bolt. It the Blade Bolts has a Wobble, then the Crankshaft is Bent. If this is Not the Case, then Send me the Model and Type Numbers Off the Engine, Please. With these I can Locate the Proper Manual and Better Assist you. Hope this Helps. I am here if you Require more Assistance. Thanks.

Good Luck

Respectfully

John

---------- FOLLOW-UP ----------

QUESTION: The shaft does not appear to be bent. the Model and type number is 12H802-2328-E1 & 99010656.  The spark plug is sooty black and the gap looks about the size of a pocket knife blade.  With the engine off the governor linkage pulls the butterfly valve wide open. When running a small spring pulls it nearly shut. If I manually open it up will running I can get a much higher RPM.

Answer
Hello Steve:

Is the Blade Bent? I have Never Heard or Seen Uneven Cut being Caused by the Engine RPM. However, on the Carburetor Issue. Go to this Addy, http://www.outdoordistributors.com/ and Select the B. Then Select Briggs and Stratton. Then Select Don't have Part Numbers. Then Select the File #12. Then Select the Folder #12H800. The Carburetor is Shown on Page 3 of 18. The Screw #98 is for Idle Adjustment and the Crew # 94 is for the Idle Air Adjustment. Turn the Idle Air Adjustment IN 1/4 Turn. If this Doesn't Helps, then Turn the Idle Up. The Black Spark Plug Tip is an Indication of the Carburetor Running Rich. The Carburetor May need to be Disassembled and Soaked Overnight and then Blow Out with Compressed Air. Install New Kit. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

Good Luck

Respectfully

John