Look on youtube for "Briggs carburetor". If it does not run, or it surges up and down in RPMs, get the diaphragm kit for about five bucks from any small engine shop, or any hardware store (the hardware store may have to order it).
The diaphragm uses the crankcase vacuum to pump fuel to the carburetor. When the diaphragm does not work good enough the carburetor does not get enough fuel. The engine runs lean and because it is lean the engine speeds up. When the engine speeds up the diaphragm supplies enough fuel. When the diaphragm supplies enough fuel the carburetor gets enough fuel and the engine no longer runs lean, and the engine runs at the proper RPMs. When the engine runs at the proper RPMs the bad diaphragm can not pump enough fuel to the carb and the whole cycle of lean with high RPMs followed by proper amount of fuel with the engine running at the proper RPMs repeats over and over again.
The cycle of high RPMs / low RPMs will keep repeating, but when it is running lean at high RPMs the cylinder and piston are being abused and wearing out faster than they should. Besides, that up down repeated revving can really get on your nerves if you understand what it is and how easy it is to fix.
Briggs engines are tough. Keep a good carburetor diaphragm on it, change the oil about every 25 hours of use, put fuel stabilizer such as Sta-Bil in it if the gas is going to be around for more than a month, and be darn sure not to hit any hard objects such as rocks, tree stumps, bricks, or tools that the brother in law borrowed and left outside when done with them, with the blade and that engine can outlast the owner.
The diaphragm uses the crankcase vacuum to pump fuel to the carburetor. When the diaphragm does not work good enough the carburetor does not get enough fuel. The engine runs lean and because it is lean the engine speeds up. When the engine speeds up the diaphragm supplies enough fuel. When the diaphragm supplies enough fuel the carburetor gets enough fuel and the engine no longer runs lean, and the engine runs at the proper RPMs. When the engine runs at the proper RPMs the bad diaphragm can not pump enough fuel to the carb and the whole cycle of lean with high RPMs followed by proper amount of fuel with the engine running at the proper RPMs repeats over and over again.
The cycle of high RPMs / low RPMs will keep repeating, but when it is running lean at high RPMs the cylinder and piston are being abused and wearing out faster than they should. Besides, that up down repeated revving can really get on your nerves if you understand what it is and how easy it is to fix.
Briggs engines are tough. Keep a good carburetor diaphragm on it, change the oil about every 25 hours of use, put fuel stabilizer such as Sta-Bil in it if the gas is going to be around for more than a month, and be darn sure not to hit any hard objects such as rocks, tree stumps, bricks, or tools that the brother in law borrowed and left outside when done with them, with the blade and that engine can outlast the owner.
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