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Briggs 12hp runs rough


Blade o' grass's Avatar
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10-21-08, 07:10 AM   #1  
Briggs 12hp runs rough

I have a briggs 12hp I/C. When I got it it did not have the tiny spring that wraps around the throttle control linkage. Would the lack of this spring cause it to run rough? I of course have fresh gas, clean carb, I adjusted carb and air/fuel mixture, new plug, air, and fuel filters.

 
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Blade o' grass's Avatar
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10-21-08, 10:15 AM   #2  
Well, I put a spring on it. It runs good for about 45 seconds, then starts running rough. When I hold the throttle linkage, it runs smooth. Anyone have any tips?

 
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10-21-08, 12:32 PM   #3  
I would check the spark plug and module for good spark. You may also want to check the valve lash particularly on the intake valve, as these engines have a tendency to loose clearance on the intake.

 
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10-22-08, 08:26 PM   #4  
Alright
I have good spark
Module is good
And vavle clearence is within tolerance
I'm still mythed

 
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10-23-08, 01:04 AM   #5  
what do you mean by running rough? Is it surging, skipping, or sputtering? Does it smoke any or all of the time? How did you adjust the high speed screw, or does it have one (what carb is on it?)?


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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10-23-08, 05:45 AM   #6  
Well, the throttle spring took out most of it, but every minute or so, when it is at full throttle with no load it seems to...."bog" out. It does not do it with the blades engaged. It only has an air/fuel screw and carb screw. Its this model.
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10-23-08, 05:54 AM   #7  
Oh yeah, it only smokes a puff on start-up.

 
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10-23-08, 03:56 PM   #8  
That carb has a high speed screw (under the bowl), an idle air mixture screw (screws in the top of the carb), and the idle speed screw (on the throttle shaft itself).

The idle mixture screw should be set at 1 1/2 turns out from lightly seated. Fine tune as needed, but it shouldn't vary more then 1/2 turn one way or the other for the final setting. If it takes more than that, it is an indication of another problem.

The high speed mixture screw should be set at full throttle. Turn the screw out until the engine starts to stumble and miss, then turn it back in until the engine begins to surge and/or die out, while counting the number of turns. Divide that number by 2 and turn the screw back out that many times and you should have it set close to the optimum setting. Fine tune as needed.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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10-27-08, 11:44 AM   #9  
Cheese,
I tried all the set screws before I checked valve lash and spark.
I replaced the head gasket and got a carb rebuild kit. The carb rebuild seemed to have do it. I think my screws were too worn. It runs great now.
Thanks every one

 
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