Lawn mower sputters and turns off within a few seconds (butterfly, weed)
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Location: East of Seattle since 1992, 615' Elevation, Zone 8b - originally from SF Bay Area
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Quote:
Originally Posted by Kenthomaz
Lawn boy F Series Mower runs for several seconds then dies. Will start up but will only run a few seconds. Hey whoever was the guy that said to spray WD-40 in to the cylinder where the spark plug goes. HE SAVED ME A MILLION ! HEY THAT REALLY WORKED ! THANKS ! THANKS THANKS !
That is a common problem when it sits all winter, the intake valve can get stuck and doesn't open or close fully. If it stays open it floods the cylinder when it sucks fuel without a spark, if it sticks closed it starves for fuel. With a small flashlight you can see both valves in most 4 cycle flathead engines. Turn it over by hand and you can see if the valves are operating correctly, then spray WD40 into the open valve with the little tube on the nozzle so that it reaches the spring area, and hand crank some more to work it in, and the problem is solved. If the valves look gummed up with varnish or carbon, spray Gumout or similar carb cleaner around the area where it seats, let it sit 10 minutes and turn over a few times. Either of these will result in a little smoke when you first start it up and it's a good idea to change the oil after it's running again.
That is a common problem when it sits all winter, the intake valve can get stuck and doesn't open or close fully. If it stays open it floods the cylinder when it sucks fuel without a spark, if it sticks closed it starves for fuel. With a small flashlight you can see both valves in most 4 cycle flathead engines. Turn it over by hand and you can see if the valves are operating correctly, then spray WD40 into the open valve with the little tube on the nozzle so that it reaches the spring area, and hand crank some more to work it in, and the problem is solved. If the valves look gummed up with varnish or carbon, spray Gumout or similar carb cleaner around the area where it seats, let it sit 10 minutes and turn over a few times. Either of these will result in a little smoke when you first start it up and it's a good idea to change the oil after it's running again.
I believe, if you check, you will find out that Lawn Boy has no valves - it is a two cycle. However; it does have a reed valve. There is a chance that WD40 would loosen up or remove some deposits on the reed valve?
Most of the time, with mowers that run and then stop, it is fuel related. Yes; there can be other issues. One of the overlooked problems with mowers that run and then stop is the gas cap. Many small engines gas caps have vent holes. If the vent becomes clogged the motor will stop when it can no longer suck gas. These vent hales are extremely small holes - almost microscopic. You need a very fine piece of wire to unclog the hole or you have to replace the cap.
Some motors also just come out of carburetor adjustment from vibration. Some small motors have no adjustment screws, some have one, some have two and some have three. If you have a mower with adjustment screws; vibration could be the culprit.
If it only runs for about 10 seconds, I would change the oil. Probably water in the oil.
IIRC, this makes the oil look greyish. This occurred with my Briggs & Stratton 190cc motor.
There is one other thing to check for with equipment that runs and then stops: The fuel line. If your equipment is approaching one or two decades old; the fuel line could be breaking down. I just replaced the fuel line on my Gravely tractor, a Weed Eater and one chain saw.
On the Weed Eater; the filter in the tank broke off the fuel line. The line also had a hole after the tank. It would run and then turn off. However; I could keep it running by giving it more choke. I also tried to open up the carburetor adjustment screw - but it kept getting worse. I then looked at the fuel line. After I replaced the fuel line it ran like new. My little Poulan 16 inch bar also had the same problems - new fuel line and it runs like new. I also have the larger Poulan 20 inch bar and had problems with both the fuel line and carburetor nuts that loosened up while running (Loctite helped that problem).
There is one other thing to check for with equipment that runs and then stops: The fuel line. If your equipment is approaching one or two decades old; the fuel line could be breaking down. I just replaced the fuel line on my Gravely tractor, a Weed Eater and one chain saw.
On the Weed Eater; the filter in the tank broke off the fuel line. The line also had a hole after the tank. It would run and then turn off. However; I could keep it running by giving it more choke. I also tried to open up the carburetor adjustment screw - but it kept getting worse. I then looked at the fuel line. After I replaced the fuel line it ran like new. My little Poulan 16 inch bar also had the same problems - new fuel line and it runs like new. I also have the larger Poulan 20 inch bar and had problems with both the fuel line and carburetor nuts that loosened up while running (Loctite helped that problem).
Not to mention the gunk and grime that can enter into the fuel tank on landscape equipment.
Wish I had you around fisheye youd get ALL my business.
If it is a Briggs and Stratton carb this is very typical. It isn't getting gas to the engine. I've had other mowers with different carbs that would start after a long winter and never needed work.
Only real solution is to either replace the carb or take it apart and clean out all of the tiny holes in the body of the carb. Chances are something is clogged up.
Not to mention the gunk and grime that can enter into the fuel tank on landscape equipment.
Wish I had you around fisheye youd get ALL my business.
Thanks! But I am getting to the point where I have fixed my equipment one or two times too many. This year I broke down and bought a new push mower - just too many things wrong with a thirty year old mower. I also bought a new leaf blower - another thirty year old piece of equipment. I am just getting tired of wasting so much time repairing and not enough time using!
Last year I bought a new Ariens tractor - but that was a mistake. Even old lawnmower people can make mistakes. For one thing; the tractor has white metal blade spindles - not a good thing for rocky soil. It also had a rod that supports the front of the mower deck. That rod has a hole in it for a spring that was on older models - not on the newer ones. The hole is the weak point for that rod and the deck will drop flat on the ground when the rod breaks - the blades can and will hit rocks, bend, and break a spindle. I also think that they put on smaller tires to cut cost - you cannot raise the blades that high off the ground (also bad for rocky soil). What did sell me on the tractor was the switch - so I could go from forward to reverse without stopping or turning off the mower blades. I think I liked the older equipment that would just outright kill you or break your ribs - I don't like safety switches.
If it is a Briggs and Stratton carb this is very typical. It isn't getting gas to the engine. I've had other mowers with different carbs that would start after a long winter and never needed work.
Only real solution is to either replace the carb or take it apart and clean out all of the tiny holes in the body of the carb. Chances are something is clogged up.
One of the biggest problems with storing equipment is leaving equipment with only a small amount of gas. Usually you will not have problems from one season to another if the tank is full. One quarter to and eighth of a tank will evaporate quick and leave gummy residue.
Briggs did have an issue many moons ago with gas tanks that warped. There was a thin diaphragm that sat between the tank and the carburetor. If I recall correctly; you would remove the tank and place a straight edge over the tank's mating surface. You would then see if the tank was warped by more than (I think) .010 of an inch. But I think they did fix that problem?
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