Briggstratton 4.5 engine fuel/air adjustment

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  #1  
Old 06-10-07, 06:39 AM
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Unhappy Briggstratton 4.5 engine fuel/air adjustment

It's a Poulan lawnmower (2 yrs old)...Could anyone tell me where to look for the carb adjustment screws or how to adjust the fuel/air mix? Engine runs way too rich...it has a floating choke valve, supposedly runs at a constant speed when running. I took the plastic carb off/ cleaned it/replaced it, replaced spark plug--seems there is no way to adjust the fuel/air mix...thanks for the help.
 
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  #2  
Old 06-10-07, 08:17 AM
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Try removing or replacing the air filter. A restricted air filter will increase the fuel ratio of the fuel/air mixture, and cause a rich condition.
 
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Old 06-10-07, 09:40 AM
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Air Filter

Was cleaned and replaced (forgot to mention in the original msg)....thanks
 
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Old 06-10-07, 10:52 AM
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I'm going to assume since it's plastic that you have a pulsa-prime carb (can't say for sure without model type and code #'s) If that's correct, there is no adjustment on that carb. First thing to check is the air filter, which you did. Next thing would be the diaphragm between the tank and the carb and the screen on the pick-up tube on the carb. Did you replace the diaphragm when you took the carb off?
 
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Old 06-10-07, 08:11 PM
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Diaphragm/gasket and fuel strainer screen

were replaced....
thanks....
 
  #6  
Old 06-11-07, 07:34 AM
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What symptoms are indicating to you that the engine is running rich?
 
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Old 06-11-07, 07:40 AM
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Rich = black smoke/soot from the exhaust and spark plug fouling....thanks
 
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Old 06-11-07, 07:47 AM
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You might recheck your diaphragm and make sure it was not distorted during assy. Otherwise it sounds as though you may have a compression issue or possibly but less likely a weak ignition.
 
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Old 06-12-07, 02:11 AM
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How did you clean the air filter and with what solution/cleaner? This should have a foam element air filter and needs to be oiled prior to use, how did you oil it and with what? Have you run the engine without the air filter in place (but with the cleaner screw in place)? Have you checked the strength of the ignition?
 
  #10  
Old 06-13-07, 10:16 AM
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I washed the filter with soap/water, then oiled it with household oil...very lightly. Is there a check of the ignition sys I can perform at home? thanks
 
  #11  
Old 06-13-07, 12:04 PM
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Ignition strength would be checked with an inline spark tester whereas you install the tester between the spark plug (keeping installed) and the spark plug wire. Rip it over and if the ignition is strong enough it will jump the large gap in the tester. Another possibility you may have is a warped carburetor body...pretty rare, but possible.
 
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