My Briggs and Stratton 3.5 HP lawn mower won't run unless I spray carburetor cleaner into the choke. Then it runs only long enough to burn off the cleaner (10 to 20 seconds). The gas tank is full. Do I need to replace the carburetor?
by 
Shady Guy
ANSWERS: 8
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No. sounds like first, replace the spark plug. it comes preset from the factory and can be purchased at auto zone. next, when has the filter been cleaned, over the carburator? this is a must, every spring before starting. oil changed lately? if its black as mud, its gotta go. the engine is running only a short few seconds, because of the carb cleaner and not receiving gasoline. is the gas fresh? leaving a can of gasoline, from one summer to another, is not a good idea. moisture can develope in both the gas can and the gas tank. If, after all the above has been accomplished and your mower will still not start.....do like i did. junk it. buy another at a pawn shop. it cost 50.00 bucks and starts every time. It saves your nerves.
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The 3.5 Briggs uses vacuum to pull fuel from the tank into the carb. The diaphragm that does this is notoriuos for drying out and failing in older mowers. This can sometimes be cured by a simple rebuild of the carb, but take into account, that as well as being able to buy a good used mower, as John pointed out, brand new mowers can be had at discount stores for around $130. Weigh that against the cost of parts and labor to fix your old unit.
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Thanks - as I think about it I maattempt to repair as a matter of pride. It's 15 years old and doesn't smoke at all because I've been faithfully cahnging oil, air filter etc every season. It's like an entity now. I appreciate your help.
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I would have to say it is the diaphragm too. If you are handy with tools it is an easy and cheap repair.
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I'm Ron Collins yes it is the diaphram I took 2 years of small engines in school e-mail me georgestrait_fan2006@yahoo.com
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Try cleaning the carby before you replace it.
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Hey, I had the same problem. My gas tank was full of rust and grime. I cleaned it out with brake cleaner and a tooth brush and then took some carb cleaner and squirted it up into both of the lines that go down into the gas tank. For me they were clogged up and cleaning them out was all it took.
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lawn mowers are pretty simple. maybe its a clogged fuel line. or a spark plug that needs cleaning. or something in the gas tank. you could clean the carburetor. now...later. what was the real problem? over a year and a half later.
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