# B&S help



## jlphoy (Apr 28, 2010)

Hello all...first post here looking for a little help with a Briggs & Stratton engine. Looked through some other threads but couldn't find help. So here goes...I have a Yardman push mower with a B & S engine. It has ran fine for a few seasons and ran fine for the first few mows this season. Then all of sudden right in the middle of a mow the power seemed to drop by about 50%. I have done all the routine stuff (oil, gas, plug, filter)...didn't help. Beyond that I'm clueless. It still mows but not well. Model # 120 K02 Type# 0418-E1 Code# 05111159 

Thanks.


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## indypower (Apr 8, 2009)

Gas tank cap could have a blocked vent. Try running with the cap loose.
The main jet (bolt on the bottom of the float bowl) could be plugged. To clean it, first drain the gas tank, then remove the main jet and clean ALL the holes. Could be 2 or 3 hole. The big one is easy to see. There is at least 1 and could be 2 tiny pin holes closer to the top in the threads.


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## jlphoy (Apr 28, 2010)

Thanks...I'll give that a shot and if that solves it. :thumbsup:


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## jlphoy (Apr 28, 2010)

Took a few days before I could get to it...but that didn't help. Anybody got any other thoughts?


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## andybcumming112 (Apr 11, 2009)

Check vavle clearances.Sounds like valves need adjusting.Do a leakdown test.


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## indypower (Apr 8, 2009)

Your engine is a flathead, meaning valves are not adjustable.
There are 2 other things you can look for.

1). Check the main jet (the bolt that holds the float bowl on) and make sure ALL holes are open. There is 1 big hole and 1 or 2 tiny pinholes in it. The tiny pinholes are the ones that clog easy and everyone misses them. 1 is located in the threads.

2). Did you hit a rock or stump when mowing? If so, the flywheel key is sheared causing the timing to be off. 1 way to tell is when you start it does it try to pull your arm into the engine? If so, key is sheared. Key only cost about $1.00.


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## 30yearTech (Sep 14, 2006)

Governor spring may not have enough tension on it. If you were mowing under any shrubs or near anything that may have contacted the front of the engine, the arm where the governor spring attaches can get bent in and this will reduce operating RPM's and cause a seemingly loss of power.


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