lawn mower

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  #1  
Old 07-25-09, 05:51 AM
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lawn mower

I have a 22" push mower with a Briggs & Stratton engine that has begun to run roughly. I replaced the spark plug and temporarily removed the air filter but it didn't help. I am also told it could possibly be bad gas, which I doubt, or a vacuum leak. Can someone please tell me what I can do to make this run well again. If it is a vacuum leak, how do I go about finding it?

Rich
 
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Old 07-25-09, 06:18 AM
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The model and type code off the engine would be helpful.

If the gas is old, it could cause rough running. Air leaks around the carburetor can be detected by squirting oil around mating surfaces and if engine smoothes out you found an air leak. Rather messy way of looking for an air leak though. You may just need to clean the carburetor.

Does running roughly mean missing or can you come up with a better description of how it is running. Does the RPM increase and decrease when it is running?
 
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Old 07-25-09, 09:17 AM
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Airman;
Try using carb or brake parts cleaner, not nearly as messy. Have a good one. Geo
 
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Old 07-25-09, 09:29 AM
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I ruled out the gas because it's fresh and the same I use for the lawn tractor. The RPM decreases and increases constantly but I'm not sure I would describe it as a miss. Up and down RPM's is probably the best way to describe it. Your idea of squirting oil on the carburetor is a good place to look. Thank you.
 
  #5  
Old 07-25-09, 09:45 AM
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Surging is a condition most normally caused by a dirty carburetor (internal). You will need to clean the carburetor and possibly replace parts. Without knowing model and type number of your engine I cannot be more specific.


Why does my engine seem to go up and down in RPM's (runs rough) ?

What are the procedures to follow when overhauling the carburetor?
 
  #6  
Old 07-25-09, 11:56 AM
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airman, what I found on the mower is as follows:

B&S 500 Series
158cc, 5.00 ft. lbs. gross tongue
3060 rpm

When I started it early today it ran pretty well for about 60 seconds then started sputtering, very much like the link I was given.
 
  #7  
Old 07-25-09, 01:57 PM
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I will guess the carb sets on top of the fuel tank, so;
You need to install a new diaphram kit, it is Briggs part # 795083 or old # 495770 also Lowe's has a kit #5083 which has the same parts.
Here we go;

Remove air cleaner, there are 2 bolts that hold things together, one on the front of the tank 3/8" and one into the block 1/2", remove these bolts, now "slowly" slide the carb/tank off the intake tube and breather tube, now tilt the tank in to release the throttle linkage and waalaa the carb/tank is removed. Check the intake tube to see if the O ring seal and plastic retainer are still on the intake tube, if so remove them and re-install them into the carb. Remove the 5 screws from the carb/tank remove carb(don't loose the spring) now spray all holes, cracks and crevases in both the carb and tank surface with brake parts cleaner, remove the main screen(looks like a thimble), now with a small screwdriver pry out the main jet(carefully) and clean it, check the O ring on the main jet for damage, if it is damaged it must be replaced, reinstall the jet, it can be difficult some times to get it to snap back in place(I use the rounded end of a screwdriver handle). Remove and clean the fuel pickup stem. Clean any junk/rust from the tank. Install the diaphram on the tank then the gasket(no goo or sealer) now carefully replace the carb(the spring will try to misalign the diaphram), tighten all screws a little at a time so as not to crimp the diaphram until they are all tight. Install the carb/tank in reverse order and you are done. If I missed something one of the real mechanics will correct me. Have a good one. Geo
 
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