lawn mower repair question

I am helping a neighbor with his push mower. He has a 6.5 HP Briggs and Stratton engine. When I prime the engine with gas using the little button on the mower, the engine starts up with no problem, but then quickly peters out. Is this likely a carberator problem? or a fuel supply problem? Are there any quick fixes that we can try. I am willing to give him a hand, but I don't really want to get into rebuilding his carb or something like that. I might be willing to clean the fuel line. I didn't notice any fuel filter on this unit, but I might not be looking at the right spot. Thanks, Paul

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Not sure if your B&S is the same as my 6.5HP Tecumseh in this respect, but bad gas and/or a loose or unbalanced blade will do this to mine. A bit of Seafoam in some new gas usually clears it up in a few run- hours.

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This is a long shot, but I once had a lawn mower that did that. Somehow, I think the air filter was completely clogged with dirt so the air intake wasn't working correctly. I removed the air filter and would start and continue to run, unlike before I took out the filter. I then cleaned the air filter and it worked okay.

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Good thing to check anyway - but generally in THAT situation, the primer won't make it run because it's already too rich.

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Pressing bulb supplies gas, so it starts. Sounds like the normal gas delivery system doesn't work since it dies out.
Google found a lot of possibilities.
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Try these Google search terms:
briggs and stratton 6.5hp starts then stalls
-or-
We've got a nice lawnmower repair place near by...maybe there's one in your area.

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If it has a paper air filter and it gets soaked with oil it will starve for air. See if it continues to run with the filter removed. If it has a carb bowl try replacing the brass screw the holds the bowl on. That way you can change it while holding the bowl in place. (You'll need to catch the draining gas in something!) . The is a large and a small hole in the bowl screw that meters the gas. The small hole is most likely plugged.

On Fri, 8 Jul 2011 14:43:08 -0700 (PDT), PaulD
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Most likely plugged fuel jets or water in the float bowl. The carburetor will need to be cleaned - which in this case will LIKELY require removaland dissassembly. You MIGHT get away with putting some SeaFoam treatment in the gas, letting it sit for a while, and then coaxing it to run with the primer until it finally draws gas through the jets - but it is LIKELY a waste of time and effort (as well as SeaFoam) in this case. If you can remove the float bowl and clean it out, as well as the jet that is part of the "bolt", THEN running sea foam through it when it starts and runs poorly will probably finish the job and this is easier than disconnecting all the governor linkages etc and getting everything back together properly if you are not really familliar with the setup.
It almost definitely will NOT have a fuel filter - and it is almost certainly a carburetor problem.

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Be EXTREMELY carefull using starting fluid. Since the engine WILL start with the primer I, as a mechanic, would NOT use starting fluid. It is reserved for when you can't get an engine to fire with any other method.
If you can get the sea foam to get to where the problem is - in the float bowl, it will GENERALLY do the job - but if the float bowl is full of gas (or water) that is not getting drwn through the carb because the jets are clogged, getting the sea foam into the carb without removing the float bowl can be difficult. SOMETIMES you can keep the engine running with the primer bulb long enough to get enough gas through the carb to get the sea-foam to where it can do some good.
If you can get it to the point that it stays running, no matter how poorly, the sea foam is always a good bet.

On Jul 9, 12:48 am, snipped-for-privacy@snyder.on.ca wrote:
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I agree that it is a clogged jet. This is an easy diagnosis since it will run for a second using the primer bulb. Fuel is obviously getting to the primer bulb, so therefore the delivery system to the carb is probably ok. But it could also be a stuck float valve (rare).
Either way, the carb has to be "gone thru" or the carb will clog again or the valve will stick again. Using Seafoam just won't cut it when you want to do the job right.
Hank <~~~ not a fan of "mechanic in a can"

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As a mechanic, I'll disagree with SeaFoam not "cutting it". It does a better job, in many cases, than going at it with a fine wire or "tip cleaner" like a lot of mechanics and wanna-bees do.
It will not harm the jet - and using a bit in the gas on a regular basis PREVENTS the problem - which even the best "skin and bones" mechanic can NOT do.

On Jul 9, 4:02 pm, snipped-for-privacy@snyder.on.ca wrote:
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Mechanics don't prevent problems, they fix and advise about problems. Preventing carb problems is the users responsibilty by keeping dirt out and keeping fresh gas running thru it. When properly maintained, no one should need Sea Foam. So, why pay the additional expense?
Hank <~~~~ anybody on the internet can call themselves a mechanic

Hank wrote:
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Because you'd get in trouble if you stole it?

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Like the Fram commercial used to say - "you can pay me now, or you can pay me tater". If you have an engine that is prone to carburetor trouble - as many on this list have indicated (by the fact of HAVING problems), running Sea Foam or an equivalent on a regular (not necessarily constant) basis makes a LOT of sense. To me as the mechanic as well as the owner. Fixing crapped up carbs is NOT an easy way to make money. Not as easy as selling the customer a new carb (which many shops do,) because if they "fix" the carb now, and 6 months later it screws up again it's THEIR problem, according to the customer. If they replace the Briggs carb and it goes bad, it's Briggs' problem - Good luck.
If, as a mechanic, I clean the carb and tell the customer to use Sea Foam in every second tank, and the customer does not, and the carb goes bad - guess what??? It's the CUSTOMER's problem - not mine. If he uses it, the chance of having another problem goes WAYYYYY down.

On Jul 9, 10:27 pm, snipped-for-privacy@snyder.on.ca wrote:
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I can't remember the last time I replaced a carb. The mechanic still has to remove the carb to replace it and then wait for the new one ot come in. It is less time consuming to just clean the old one. Time is money. When cleaned properly, they should be as good as new. When maintained properly, they should last way more than 6 months without any additives.
If Seafoam is such a good thing, why don't the manufacturers reccommend it?
Hank <~~~~ not a parts changer

I can't remember the last time I replaced a carb. The mechanic still has to remove the carb to replace it and then wait for the new one ot come in. It is less time consuming to just clean the old one. Time is money. When cleaned properly, they should be as good as new. When maintained properly, they should last way more than 6 months without any additives.
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The same reason most auto manufacturers don't want you to work on your car opposed to bringing it in for service, they make money from their dealership service.

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I've never had a problem either. It amazes me how many cars sit around on car lots for months and never seem to need any additives. Do you think it is because they start them up and move them occasionally? :-)
Hank

Hank wrote:
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Yes, many (most) lots start cars regularly.

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But that's not the main reason. See my previous post re: emmission controlled fuel injected vehicles.

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No, it is because automotive fuel systems are SEALED, and fuel injection systems very effectively limit the contact between fuel and air.
There is NO evaporation, NO moisture attraction, and NO oxidation in an emission controlled, fuel injected, automobile.
All cars built in the last 25 years are also built with E10 fuel in consideration - no parts that are not compatible with E10 are used.

On Jul 9, 4:02 pm, snipped-for-privacy@snyder.on.ca wrote:
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You must have stock in seafoam. I never use it Small engines were designed to work fine on just gas.
Since it starts by priming it the gas is fine.
The carb is messed up. Most B&S use a conventional float bowl style carb. Either the gas is not able to enter the venturi via the jets from the float bowl or the float valve is preventing the gas from filling the float bowl. You might be able to pull the float bowl and clean it out without removing the carb. The float and it's needle valve may be removable with just the bowl off. You can spray some carb cleaner up the jets if the bowl comes off. Also you can check and see that gas comes out when the float is down. Otherwise I'd take the carb off. Occasionally you can unstick a stuck float by banging a bit on the side of the carb with something like a small piece of wood or the handle of a tool so I'll try that on no gas situations.