6HP Briggs & Stratton Model 12H802-2684-B1

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  #1  
Old 08-03-10, 04:29 AM
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6HP Briggs & Stratton Model 12H802-2684-B1

Have a Craftsman 917.387620 22" mulcher with a Briggs and Stratton 12H802-2684-B1 6HP that is 7 - 8 years old and has been running flawlessly.

I left it in a leaky roof part of my garage and it got some water on it which I dumped off. Took it outside to run it and it barely ran, choking and sputtering, but continued to run. I noticed when I tilted it forward on the front wheels, it ran normally. Then when I lowered it, it sputtered again. Thought maybe water was shorting out the magneto.

Thought I maybe had water in the gas so I dumped it out. Put in new gas and it ran better, but still bad. As it ran longer, it got increasingly better until it was back to normal. That was a week ago. Put it away in a dry place this time.

My wife used it yesterday and it ran fine for awhile and then the rpms took a dive to something lower than the right speed and got some roughness in it and loss of power. No black smoke, just roughness Sounds like it's muted when it runs.

Changed the plug...took off the bowl and cleaned it. Checked the float for cracks and shook it. No rattle. Checked the float valve pin was OK and clean. Checked the main jet (bottom bolt). The through hole and the one down the middle seem to be clear. Took a small sewing needle and cleaned what I could but didn't see any appreciable dirt. Bowl gasket is OK and the valve needle travels freely. Can feel it seat on the rubber seal when holding the float up. Oil level is OK. Put in new air filter. I was ready to buy a new float and a new main jet, but the ones in there really seem to be OK. No leaks in the float and no dirt I can see in the main jet.

I seem to have OK spark, but I'm wondering if I have a bad magneto issue or some dirt lodged in the carb. I put in some STP fuel system cleaner and ran it, but still runnng lower power than full, lesser rpms than normal and with a tad of roughness.

Any ideas would be appreciated. Thanks.
 
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  #2  
Old 08-03-10, 10:40 PM
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Tough one... sounds like you did everything that should have been done. It sounds like there is water in the bowl to me, even though you drained it. Check it again, and clean the carb passages with carburetor cleaner in a spray can from tan auto parts store. See what that does for it.
 
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Old 08-04-10, 05:30 AM
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I took the bowl off a couple more times and drained all the gas out of the line. I put carb cleaner in the gas and let it sit and run the way it is running and it continues to run the same, slightly rough at a slightly reduced power/rpm.

It sounds like when it was OK, just after it starts and it's climbing up to operating speed only doesn't quite get there.

If I can't get it straight, I'm thinking of replacing the carb.
 
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Old 08-04-10, 09:05 AM
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Originally Posted by Ejectr View Post
I took the bowl off a couple more times and drained all the gas out of the line. I put carb cleaner in the gas and let it sit and run the way it is running and it continues to run the same, slightly rough at a slightly reduced power/rpm.

It sounds like when it was OK, just after it starts and it's climbing up to operating speed only doesn't quite get there.

If I can't get it straight, I'm thinking of replacing the carb.
It is possible the governor spring has stretched, might try bending the tab it hooks into forward a little, Have a good one. Geo
 
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Old 08-04-10, 06:20 PM
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George: It's hard to explain the sound. The speed is lower than it should be and it sounds a little rough and starving some power and smoothness. It's not just a low rpm. It's a doggy sound.

I can pull on the spring and it readily increases rpm, but with the same slight roughness and starving for power sound. It's just not smooth sounding.

That's the trouble with forum boards. You can't put a rrrrrr sound in it so you guys can hear the motor.
 

Last edited by Ejectr; 08-04-10 at 07:00 PM.
  #6  
Old 09-19-10, 08:41 PM
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After the extensive search you've already done, I would check for any air leaking into the system. Start with the fuel hose and look for cracks and follow through to the carb gasket.
 
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Old 09-20-10, 08:10 AM
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With the engine running spray/dribble some carb/brakkee parts cleaner behind the carb on the mating surfaces, if the engine tempo changes you have an air leank. Have a good one. Geo
 
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