Need help - Briggs and Stratton Lawn Mower

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  #1  
Old 10-24-04, 06:20 PM
balladish
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Need help - Briggs and Stratton Lawn Mower

Hi All,

I bought a used B&S 4hp Quatro engine lawn mower, model number 122702. When I inspected the engine at purchase time, it started up without a problem, but had trouble idling at anything but choke position. Not knowing much about lawn mowers, I bought it. I proceeded to mowing my lawn, which took about 45 minutes. I then ran out of gas. The tank was empty for about 3 days until I got around to filling my portable gas tank. I filled it up with 92-premium gas at the pump, and filled the tank with it. It wouldn't start at all. The only way to get it to work was by tilting it to the right - the carburettor/air filter side - and shaking it, at which time it would start, but then die down as soon as I placed the mower back on level ground. If it's on level ground I can't start it at all. I contacted the owner, who said I shouldn't have put in 92, I should replace it with 87 regular gas. I drained the tank and did that, but I still have the same problem.

The air filter is dirty, but even with the filter competely off I can't start the engine unless tilted on its side and shaken as illustrated above. I checked spark plug - gab and condition look OK. I performed an oil change, no change.

Can anyone help me here? Thanks in advance!!
 
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  #2  
Old 10-24-04, 06:36 PM
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balladish
It sounds like a fuel delivery problem...possibly the float is sticking and not allowing the bowl to fill completely.

When you shake it, it probably moves the float around allowing fuel to fill the bowl. I would recommend to remove the float bowl, and either check the float or change the needle and seat to see if that makes a difference.
Yes the 92 octane is more than you need but that's not the cause of the problem. These motors are designed to run on 87 octane....any more is a waste of money.
Try this and let us know.

snoman
 
  #3  
Old 10-24-04, 06:42 PM
balladish
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Thanks for the reply.

Could you point out the location of the float, bowl and needle? Are these components of the carburettor?

Sorry for my ignorance, and TIA.
 
  #4  
Old 10-24-04, 11:07 PM
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Yes, they are. I don't think your engine has these though, because you probably have a diaphragm carburetor. Is the tank made of metal, with the carb bolted to the top of it?
 
  #5  
Old 10-24-04, 11:18 PM
Azis
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I think more likely than the float sticking is when you tip it gas is able to seep into the throat of the carb just enuff to start it up.
On the bottom of the carb is a can or bowl, in the bottom center is a bolt. Be aware that when you remove the bolt and the bowl any gas in the tank may come out. When you take the bowl off you will see the float and be able to move it up and down (or should) The bolt that you removed holding the bowl on, there are two holes on the side and one on the end, make sure these are clear. Check for travel on the float, if it doesnt seem to hang it shouldnt stop fuel from getting to the carb. Clean any garbage in the bowl and put er back.
 
  #6  
Old 10-25-04, 08:21 AM
balladish
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Thanks all for your help.

Azis, you were right on. The little holes in the carb bolt were all clogged up. Cleaning that out and refilling the tank solved my problem. It now idles nicely. Thanks!
 
  #7  
Old 10-25-04, 10:18 AM
Azis
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Glad you got it...actually I first had the same thought as Cheese, luckily you posted the model # of your tool and I was able to pull up a manual to verify.

Just a note on fuel octane....Small engines are indeed designed to run and operate on regular unleaded pump gas (87 octane) and with the price of gas now a days well.....
Higher octane is meant for higher performance engines usually with higher compresion ratio's. Compresion causes heat, the higher the compresion the higher the heat, lower octane fuels combust at a lower temp and can ignite under compresion before the spark plug fires to burn the mixture (pre-ignition, detonation, pinging) Generally aircooled engines are more susceptable to this as engine temp is not regulated
It is my opinion that higher octane fuel does increase performance and burn cleaner, while it wont be noticeable on your push mower while putting around your yard, it may well show up over the life of your mower in the combustion chamber by burning cleaner and more effeciently less deposits fewer problems. If the average homeowner used 10 gallons in a season, the added cost of .10-.15 a gallon.......????
With all that said, when I go to fill my pail I pull the nozzle that takes the fewest quarters
Hey I work on Lawn Mowers not the Space Shuttle
 
  #8  
Old 10-26-04, 02:19 AM
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Thanks for looking up the #s Azis! I didn't, lol. You don't often see a Quattro with a bowl type carb.

A side note: The octane in fuel actually decreases performance, contrary to popular belief, in an engine made for regular unleaded. Octane is added to slow the rate of ignition of the fuel. This is necessary in higher compression engines to reduce pre-ignition (spark knock, or what some people inaccurately refer to as "valves rattling"). The ignition occurs just before the piston reaches the top-most point of it's travel in the cylinder. The fuel enters even before the ignition. If the engine compression is high enough, and the engine is hot enough, it will ignite the fuel before the spark plug fires, and the explosion of the fuel collides with the top of the piston, which is still moving upwards, creating the ping sound of pre-ignition. Higher octane fuel will not ignite as quickly or burn as fast, thereby reducing/eliminating the problem. Some small engine manufacturers have even noted that mid and high grade fuels should not be used. I don't necessarily see any harm in it, but it actually reduces the performance of the engine, although it will be unnoticeable.
 
  #9  
Old 10-26-04, 12:05 PM
Azis
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I would have to agree Cheese in this case, my experience and training is more refereced from larger air cooled engines where Carberation and valve train become much more a part. Higher octane fuel is required to achieve increased performance, where the slower burning is translated into additional low end torque and cooler operating temps, still, as you stated, unoticeable to the operator.
Heehehehe ok I got some O-Rings to check on the shuttle
 
  #10  
Old 10-27-04, 01:28 AM
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Quote: "Heehehehe ok I got some O-Rings to check on the shuttle "

Oh my!!!! LOL! Isn't it odd how a thirteen cent "O" ring can be soooo very important??
 
  #11  
Old 07-01-08, 11:16 AM
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We have purchased several new lawn equipment items, such as weed eaters, lawn mowers, leaf blowers, and chain saws only to have many things go down in about two to three months time, not operable at all.

We've found out that the problem is ethanol in the gasoline. We have one readily available source for additive free, pure gasoline, which is our local airports, the problem being with them is they only have 100 Octane and that we hear has a problem with efficiency; that these small mowers will lose power with them, but gas from sevice stations will ruin everything, as ethanol bonds with water and ruins engines, and the ethanol eats up anything that is fiber-glass, plastic or rubber, so what does one do when your livelihood depends on equipment that runs and runs well?

A girl at the airport tells us that she noticed a station that put up a little sign that they have ethanol-free gasoline, so we are going to check it out today. If not, it's going to be $7.95 a gallon gasoline, which is still cheaper than losing jobs and/or paying for new equipment and/or repairs.

Here's hoping.

Sandi
 
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