does not speed up like it did. Also the sparkplug is fouled with a dry black soot
Craftsman

Experienced gardeners share their insights in answering this question :
Check air filter, check carb adjustment sounds rich

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If your Briggs & Stratton engine has a spark but won`t run, then it is most likely a problem with the gas or air intake in the engine. The spark on the spark plug ignites the gas in the piston, but if the air filter is clogged or the gas can`t flow, then the engine won`t start.
The most common reason for a surging lawn mower engine is a blockage in the fuel supply, but there are other possibilities: Bad gas. Bad spark plug. Dirty/faulty carburetor.
If your lawnmower`s engine is surging it could be a problem with the carburetor. The carburetor mixes air and fuel to the perfect ratio for combustion. There are passages and nozzles (called jets) that route the fuel through the carburetor. The jets meter the precise amount of fuel that is needed for combustion.
Lawn mower surging is a result of either bad gas or spark plug, dirty air filter, or clogged gas cap vent. A dirty carburetor jet and fuel filter might also be the reason. You can also consider a carburetor gasket leak, which can be fixed by an engine starter spray.
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.
Bad Spark Plugs

If the engine holds compression well, and the fuel system is working correctly, but it still won`t start, that tells us that your car`s spark plugs may not be working. The spark plugs ignite the air/fuel mixture inside the engine`s cylinders. It`s the resulting explosion that actually powers your car.

The problem may involve an annoying change (up/down) of engine speed while cruising at a steady pace, a low drop (or even cut-out) at idle or when approaching a stop, a wild high engine speed of several thousand rpm followed by a drop to near zero, etc.
Stale fuel, dirt, and debris are the most common cause of outdoor power equipment not starting or running properly. If you store equipment with untreated gas in the tank, it can lead to engine damage.

Discover Relevant Questions and Answers for Your Specific Issue

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Help with the lawnmower. It starts and stalls after a few seconds
ANSWER : Check the fuel system clean the carb .

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I have had a poulan pro 550 series push mower for almost 1 year at the end of the season last year the mower would start briefly and then stop. i have cleaned out the air filter and that did not help.the mower started, i made one revolution around the yard 3/4th of the way the mower quit. I then primed the mower it started then quit and now it will not start at all. Does anyone have any suggestions of what to do. Thanks
ANSWER : There is a little spring that works the carburetor arm. If that popped off then the mower will not run.

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I have a problem with a Black and Decker electric lawn mower model MM525. While cutting some high grass today, the mower slowed down, then quit and would not restart. I checked the electrical outlet and there was no power–the fuse was burned out in the switch box. I replaced it, tried again, and again it would not start or even give any response at all, but again it blew out the fuse in the box. The fuse is 25A and the mower is only 12A so that’s not an issue, besides, I’ve used this mower from that outlet for about 4 years since I first got the mower and never had any problem before. My question is: is whatever is causing the mower not to start and to blow out my fuse something that can be repaired or should be? Thanks.
ANSWER : Hello blumph,
I can think of only one or two things that are causing your problems. It could either be approx. a $14.00 switch in the handle that has shorted out, or 2 bad brushes $1.75/ea.on the armature (motor). Both are fairly simple fixes with just a screwdriver and maybe pliers. You might also check and see if the power cord has been chafed or damaged and is shorting out. See below for parts:http://www.ereplacementparts.com/black-and-decker-mm575-electric-lawnhogtrade-mulching-mower-parts-c-4167_9514_9550.htmlyurcarguyken@yahoo.com

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I have a Poulan push mower that after mowing in a ditch started making a loud noise and running rough. It almost sounded as if metal was hitting metal. The mower was vibrating more than normal. I checked under the mower and nothing is hitting. After a few times of stopping the mower engine because it sound as if it is going to die down the mower will not start now. The shaft does not appear bent and the blade appears ok. The mower has oil, a good spark plug and a clean air filter. It was running fine until that moment. I did not see anything that I hit but it is possible I hit something in the ditch like a pine cone or branch. What could the problem be and how would I go about fixing it?
ANSWER : If you are sure the oil level is correct then it sounds like it’s about to die, unfortunately. A pine cone shouldn’t cause any damage, but a large branch may do so. Was it smoking before you shut it down? The vibration could be caused from a bent blade. It could also be caused from a part breaking in the motor. I wish I could have given you better news!

Good Luck,

Jim

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Hi i having a problem starting my mower it a Craftsman LT2000 18.5 Intek OHV Briggs & St i removed the battery and starter and had them both check both are…
ANSWER : Turnes over slow for 2 or 3 turnes then quick and maybe a start or goes bact to compression on engine

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Craftsman riding mower lt-1000 leaks gas – Craftsman 17.5 hp 42 in. Deck Lawn Tractor – CA Model
ANSWER : Need to fix that. it may be a fire hazard.

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I have trouble starting a toro walk behind mower
ANSWER : All, I thought my carb was shot, so I replaced it. Still, start but no run (and had to use starting fluid). THEN!!! I noticed the spring to the “rev limiter” (just below and towards rear of carb) was not “tight”. The stupid bracket that holds the end of that spring had been bent down ~1/16″ and that caused all this heartache. CHECK YOUR REV LIMITER!!!

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My Toro mower with a Briggs & Stratton engine starts and then cuts off after a few seconds. How do I fix this?
ANSWER : If it starts on choke and then stops may need to clean out carby and fuel tank

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