es at a excessively high speed and wont throttle down.
Briggs & Stratton

I cleaned Carburetor and adjusted valves first. It still backfired through exhaust and carburetor between 1/2 and full throttle. Then i adjusted governor, the shaft only turned about 1/16. Now it idles at excessive high speed and wont throttle down, but it does not backfire or surge. Its a 25 HP 466777-0165-E1
Experienced gardeners share their insights in answering this question :
You adjusted your governor incorrectly.

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Gasoline that contains alcohol has a tendency to ignite easier, which can cause afterfire. Small engine muffler type and manufacture. Carburetor adjustment may not be properly set for correct engine performance. Anti-afterfire solenoid may not be working properly.
When surging or inconsistent power occurs in your generator, fuel could be the cause. Should you experience this, checking fuel levels can be a great first step, but your dealer or service provider can check all fuel system components preventatively.
If the spring is set in the wrong position it can cause the engine RPMs to surge. Over time the spring can stretch out, causing the same engine surging. Often surging caused by the governor can be fixed by simply adjusting the governor spring. It usually only takes a small adjustment to correct the surging.
You Lose Power in the Middle of Mowing:

Here`s why this happens and what you can do: Dirty Air Filter on Your Lawn Mower: Clean or replace. Dirty Spark Plug: Clean or replace. Build Up of Clippings & Debris: Clean underside of your lawn mower deck as noted above.

Excessively lean carburetor settings can contribute to backfiring. If the mixture is too lean, it may burn very slowly and unevenly. This condition, in turn, may result in burning mixture remaining in the cylinder until the beginning of the next intake stroke when it can ignite the incomming air/fuel mixture.
Surging and Lagging

Another good indication that your spark plugs are dirty or worn is if your vehicle experiences surges of speed, resulting in a jerking acceleration. These surges occur because your spark plugs are not igniting the fuel in your engine at the proper rate, resulting in an uneven speed.

It can be caused by various factors, fuel injection problems, bad spark plugs, a malfunctioning air sensor, might be a dirty air filter, and troubles with the engine control. Other issues of the fuel ignition system can also trigger surging when stopped.
If an engine is not getting enough fuel (this is called “running lean”), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge.
Engine hunting and surging at idle is usually caused by a fuel delivery, air leak, or governor system problem. Cleaning/overhauling the carburettor, adjustment of the governor, and/or changing the air filer may be required.
Replace dirty or clogged fuel filter. Replace old gas with fresh gas (properly dispose of old gas). Check oil level and add if low. Adjust cutting height of mower before cutting tall grass.
There`s a variety of factors that can cause your car to backfire, but the most common ones are having a poor air to fuel ratio, a misfiring spark plug, or good old-fashioned bad timing.
If too much fuel is added to the engine, it may not all burn up before the exhaust valves open — letting unburned gasoline into the red-hot exhaust headers, where it can combust and lead to a backfire. Too much fuel could be getting into your engine due to damaged and leaking fuel injectors or bad engine sensors.
Explanation. Common causes of backfire are running rich (too much fuel going into cylinders) or faulty ignition, possibly a fouled (dirty) spark plug, coil, or plug wire. Pop-backs are usually caused by problems with timing.

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ANSWER : All the pictures I have of this carb show two adjusting screws.

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Won’t crank over seems like to much compression ?
ANSWER : OHV? First try adjusting the valves too much clearance will the decompressor to not work. Now the decompressor can also fail but try the valve adjustment first.

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Hard hitting on compression stroke when starting
ANSWER : If its the 21 or 20 hp OHV single briggs. Adjust vales to .004. The cam also has a decompression that breaks, Causing hard start. So if valves are adjusted and u still have problem. “Could” be cam, remove bottom cover and inspect cam. new cam about 75 to 100 bucks.

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I have A briggs & stratton 300 engine. When I start the motor surges at idle and full throttle.
ANSWER : Needs a new diaphragm between the carb. and tank…..cost about 2-3 dollars…(remember how it goes back on, you have a rubber piece and a firm gasket piece…the rubber piece mounts on top of the gas tank first, then the gasket piece on top, then the carb., then mount the carb. in with the five screws..(blow out all the ports when it is disasembled.)

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ANSWER : Sounds like the carb needs to be rebuilt

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<!– from fixya rte –>Backfire, and will not restart – Briggs & Stratton Briggs Stratton Lawnmower Lawn Mower Short Block
ANSWER : Lost valve seat my have to short block engine take in for valve job but be prepared if thet say your need a short block valve job 150 .00 to 200.00 short block 600.00 tp 800.00 dallars

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When I start it the engine surges. When I pull the handle on the wand the engine will not go to max rpm.
ANSWER : Check to see if the choke is not on.

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The engine surges at idle and then does not run constantly underpressure. sounds like fuel but cleaned all lines and used new fuel. any suggestions
ANSWER : A new spark plug and don,t forget to push in the choke after start.

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