Briggs and Stratton runs slow

fishandbrewDecember 27, 2007

I have a B&S 12f700 series engine on a John Deere 14PZ push mower. It's been running slower and slower and losing power. Today I cleaned the carb and replaced the soft goods and float pilot. This is the prime carb, not the choke model.

It took a while to start, and once started, it is running at just above idle speed and won't take any load at all. The governor seems to be working (it's free and will reposition the throttle linkage), but the engine won't run full speed. If I override the governor, it will run full speed.

I know that there is probably information that I have omitted, but I can fill in if necessary.

thanks,

Mike

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tomplum

It would likely be your throttle able adjustment or the linkage got bent in the front.(happens enough on these)Assuming the spring doesn't look damaged and is connected, and the cable adjustment is ok. Adjust the linkage. The linkage will adjust by bending the tab forward or it will have a torx screw on the front. In the perfect world, you would have a tach- but adjust by engine sound err on the cautious side rather than overspeed.

    Bookmark   December 27, 2007 at 10:49PM
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fishandbrew

Thanks - the linkage has gotten bent a couple of times. I'll give it a try when the weather clears.

    Bookmark   December 28, 2007 at 2:56PM
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fishandbrew

Well, weather cleared up, straightened out the linkage and speed did come up. Now it won't take load. As soon as it hits heavy grass, it dies. It's like the governor isn't working. The spring is in place and all the linkages are intact. The governor seems to be hunting somewhat with no load.

    Bookmark   January 6, 2008 at 11:05AM
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tomplum

The hunting of the governor would indicate that it is running a bit lean. Ensure that the intake is tight and the gasket and new seal is in place. If the seal wasn't new before, make it new. Be sure that the carb mounting bracket has all its bolts in it. The older models had a HS adjustment screw just above the float bowl towards the front of the engine. Turn it out 1/4 turn and fine tune from there. Fuel also needs to be fresh- hopefully w/in 1 month old. If all that seems in order re-clean the entire fuel system complete.

    Bookmark   January 6, 2008 at 11:43AM
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