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Re: Engine runs wide open regardless of throttle...
Check that the ACTUAL position of the throttle plate closes off the carb bore. Often the actuating mechanism slips on the shaft on aome motors due to a loose clamp.
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There is no variable throttle control for this model i.e there is no lever for engine throttle on the handle bar?
If yes, then engine speed is fixed and open throttle is normal.
The motion of the linkage is merely movement of the governor mechanism. Wide open is normal when engine is not running. The governor will close down the throttle as engine starts and reaches the fixed operating speed. There will be adjustments but on a fixed speed model only the running speed is considered adjustable.
The MTD engine service manual is available at the following URL for no fee.
Can you Regulate the Engine Speed Using the Governor Arm? If Yes, then Reset the Governor. **To Reset the Governor; Loosen the Governor Arm Bolt and Turn the Governor Shaft Clockwise Until it Stops. Using the Governor Arm Hold the Carburetor to Full Throttle. Now with the Shaft Full Clockwise and the Governor Arm and Carburetor Held at Full Throttle, Tighten the Governor Arm Bolt. If the Engine Still Runs Full Throttle, then Reverse the Rotation of the Governor Shaft, but Still Hold the Carburetor at Full Throttle with the Governor Arm. If it Still Runs at Full Throttle, then Check the Internal Governor.** If you Can Not Regulate the Engine Speed Using the Governor Control Arm, then Check the Carburetor Throttle Valve. If the Throttle Control Valve (sometimes called a Flap or Plate) Mounting Screws Came Out of the Control Valve, then you will have No Control Over the Engine Speed. Send me the Model and Type or Spec Numbers Off the Engine, Please. With these I can Locate the Proper Manual and Better Assist you. **The Throttle Cable Attaches to the Throttle Control Bracket. The Cable Moves a Slide that Moves a Pivot. The Pivot has the Spring Attached to it and to the Governor Arm. The Solid Link Connects to the Governor Arm and goes to the Throttle Shaft on the Carburetor. When the Throttle Cable is Moved it Moves the Pivot and the Pivot Pulls the Spring. The Spring Pulls the Governor Arm and the Governor Arm Moves the Throttle Shaft. Usually the Spring is in the Lower Hole in the Governor Arm and the Solid Link is in the Top Hole of the Governor Arm.** If you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens
Try a static governor adjustment first as it simply be out adjustment.
Static Adjustment Procedure
Make this adjustment whenever governor arm is
loosened or removed from cross shaft. Adjust as follows:
1. Make sure throttle linkage is connected to governor
arm and throttle lever on carburetor.
2. Loosen nut holding governor lever to cross shaft.
3. Move governor lever toward carburetor as far as it
will go (wide open throttle) and hold in this position.
4. Insert a long thin rod or tool into hole on cross shaft
and rotate shaft clockwise (viewed from end) as far
as it will turn, then torque nut to 6.8 N·m (60 in. lb.).
Are you asking how to reset governor linkage to factory spec? If so, move governor arm in direction that opens throttle valve on carb wide open. Hold in this position. Loosen small nut on bottom of governor arm. With a needle nose pliers turn center arm that goes into engine in the same direction you turned governor arm to open throttle valve. Holding in position, now tighten nut on governor arm tight again. This is referred to as a static setting and is factory spec. Good luck!
Make sure the throttle shaft is not stuck in the wide open position. You may also make sure the throttle plate is attached to the shaft, these have been know to come loose and if the shaft moves the plate does not move with it. You may have an internal governor problem, but it is best to eliminate all outside possibilities before pulling the engine down. There is also a "static" adjustment that can be made to the governor but you may want to see a service manual to perform that operation.
It sounds like the govenor spring has become disconnected or the clamp on the governor shaft has become loose and allowed the linkage to get out of adjustment. If problem has occurred suddenly it could mean the governor gear assembly inside the engine has broken and means the engine will need to be dismantrel to replace the governor gear assembly.
Check throttle linkage to see if spring is attached at both ends, one end on the throttle linkage and the other at the fixed point on the engine or to the end of the speed control lever. With engine stopped the spring should hold the throttle wide open and hand pressure on the linkage shoud be all that is needed to move throttle shaft closed to the idle position with no binding in the movement of the linkage.
If spring is OK and while engine is running, linkage should be able to be be moved to bring engine back to idle. If porblem has occurred gradually, then linkage will need re-adjusting. Loosen adjusting clamp on governor shaft, then holding linkage in wide open throttle position rotate shaft as far as it will go in the opposite direction to that requred to close throttle to idle . Re-tighten clamp.
Check to see if the throttle shaft on the carburetor is actually moving (with engine off) Does it slow down when you move the throttle control on the dash? Start it up and try moving the linkage on the governor shaft, if there is little or no resistance but the engine slows when you move it, most likely you have a broken governor gear inside the engine. Another possibility is that the screws that hold the throttle plate to the shaft have come loose and the plate is jammed in the throat of the carburetor
check the lever biside the mower that connects to your carb. move it by hand while running if no change the governor has broke,, need to take engine off and replace, but if you move it and it slow down change spring
The Carbuertor Throttle is Held in the Full Open Position Until the Engine is Started and Running, then the Governor and Spring Work together to Keep the Engine RPMs to the Desired Setting.
The Following is an Explaination on How the Governor System on Small Engines Function.
>>The Governor System behaves like an Unending Tug of War between One of Two Governor Springs, which Pull the Throttle Toward the Open Position, and a Spinning Crankshaft, which Tries to Close the Throttle. When the Load on the Engine Increases - a Typical Example is when you Move your Running Lawn Mower from the Driveway to the Grass - Crankshaft Revolutions Drop. But the Governor Spring is Still Tugging, Causing the Throttle Plate to Open. In Response, a Larger Volume of Air-Fuel Mixture Enters the Carburetor, Increasing Engine Speed to Compensate for the Increased Load. The Crankshaft Speeds Up, and the Tug of War Resumes, until a New Equilibrium is Achieved. With Each Change in Load, the Tension Between the Governor Spring and the Load Brings about a New Equilibrium, known as the Engine's Governed Speed. Neither Side Wins until the Engine is Shut Off. At that Point, without the Crankshaft Spinning, the Governor Spring Pulls the Throttle to the Wide-Open Position. Two Types of Governors are Common on Small Engines - Mechanical and Pneumatic.
Please, Do Not Hesitate, If you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Be Happy. Thanks.
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