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B&S Mower stops

AndyK's Avatar

Join Date: Jun 2009
Posts: 13

04-25-10, 04:49 PM   #1  
B&S Mower stops

Toward the end of the last mowing season my MTD rider, 15.5 hp B&S motor would run absolutely great for the first 30-35 minutes, then would start to sputter and die. It would run OK at about 80% of full throttle. I've replaced the plug, fuel line, fuel filter, bought a cool tool that shows the spark when the engine is running, used about 10 oz. of Seafoam gas treatment in a gallon of gas, and still can't figure out what's wrong. The same problem has returned this year.

I would appreciate any advice.

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SeattlePioneer's Avatar
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Join Date: Jul 2007
Posts: 5,503

04-25-10, 08:33 PM   #2  
I'm no Xpert, but I checked my B&S manual to see what causes for "Power Loss" they list.

These include:

1. Bind or drag in unit ---if possible disengage engine and operate unit manually to feel for any binding action

2. Grass cuttings building up under deck.

3. No lubrication in transmission or gear box.

4. Excessive tension may cause seizure.

It's probably something else, but I thought I'd mention these possibilities.

hopkinsr2's Avatar

Join Date: Feb 2005
Posts: 1,561

04-25-10, 10:15 PM   #3  
Seattle has some excellent points, Some I wouldn't have thought of,,, But the first thing that comes to mind (after 30 mins of running) is the Gas cap not venting & creating a vacuum in the fuel tank... Try running it with the gas cap loose (if it doesent spill fuel everywhere) & see if that helps... On another thought,, Do you have to boost it to start it?? If so the battery & charging system may need attention to supply enough volts to keep the fuel shut-off solonoid open,,,... Roger

Last edited by hopkinsr2; 04-25-10 at 10:21 PM. Reason: more info
cheese's Avatar
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Join Date: Jul 2001
Posts: 16,574

04-26-10, 12:11 AM   #4  
I agree with the gas cap as being possible culprit. If not, drop the carb bowl and check fuel flow from the tank into the carb.

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

God bless!

bcroe's Avatar

Join Date: Feb 2008
Posts: 15

04-26-10, 12:34 PM   #5  
Kohler Loses Power

When that happened to my 20 hp Kohler, I put a fuel pressure gauge at the carb inlet. The engine uses a pulse type gas pump. Pressure should be around 3 psi, but it dropped off. An outboard tank cured it; I found grass clippings had gotten into the fuel tank outlet and nearly closed it. Bruce Roe

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