Briggs 5 HP Engine Surges

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  #1  
Old 06-08-09, 05:43 PM
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Question Briggs 5 HP Engine Surges

Briggs
Model 12H802
Type 0661-01
SN 97032558

Working on 5.0 HP Briggs w/primer bulb (no choke). Removed & Cleaned carb by soaking it in can of carb cleaner and then compressed air.

New spark plug & Air Fliter. Starts easy. However, engine surges (revs up and down) "moderately" all of the time. Mower will cut grass ok.

There is no idle adjustment screw/spring. There are no needles on the carb you can adjust. Internal governor. Governor arm moves freely.

Just wondering what can cause a mower to surge and if there is anything that can be done about it. Is this typically a carb/fuel delivery issue or a governor issue?

Thanks.
 
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  #2  
Old 06-08-09, 05:57 PM
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Sometimes you get a tiny piece of crud in the carb from a dirty air filter and it will surge and generally it will just work itself through.

Does it have a fuel filter? Sometimes a clogged filter will cause surging. It may loook clean but could have some fine particles in the mesh and restrict the flow.
 
  #3  
Old 06-08-09, 07:08 PM
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Air filter is clean and new. No fuel filter. Sounds like i need to remove carb and clean again.
 
  #4  
Old 06-08-09, 07:30 PM
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Surging is usuually because engine is starving for fuel or sucking in air. Re-clean carb and also check intake manifold (prone to cracking), carb to intake O-Ring and air cleaner gasket. If you did not replace that, I would PN# 272653S, install it to air cleaner base, then install base to carb. To check if it is O-ring or AC gasket, while it is surging spray some carb cleaner at each location, if surging goes away while spraying, you found your problem.
 
  #5  
Old 06-08-09, 08:12 PM
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Bowl nut aka high speed jet

Did you also soak the bowl nut? The small orifice in the center of the bowl nut can be partially blocked and cause surging. these deposits can be so hard that you will think that the hole is smaller than it is.

AJ
 
  #6  
Old 06-08-09, 08:41 PM
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Great Suggestions. I do that tomorrow,

Thanks!
 
  #7  
Old 06-10-09, 02:59 PM
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The problem was the o-ring between the carb and the engine. It had been on there so long that it had flattened out. I replaced it with new o-ring and problem was solved.

Thanks for the help and suggestions.
 
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