This mower has an odd history, but appeared to be in good shape. It was given to me by a friend, who picked it up from the curb in his neighborhood (it's a nice neighborhood). I don't know if he found out why it was being tossed out. He just picked it up as a repair project to do with his son, and then found out I was looking for one, and offered it to me.

It's a Briggs & Stratton 6.5 Hp engine. Looks to be only a few years old and in good condition. Friend put in a new air filter, spark plug, and I think also changed the oil. I checked the oil and it looks cleaner and new-ish.

I've used it several times this year. It's been running great, starts right on the first pull. Suddenly at the end of my last session, the rpms dropped but it kept running. When I turned it off I could smell gas a bit. Next time it started fine, but is still running slow. I managed to finish the yard with it running slow.

I've check the air filter and spark plug. Both look clean. There was a little oil or gas residue at the bottom of the air filter. There was a little oil on the threads of the spark plug screw, but the sparky end was clean.

I'm just trying to see if there's anything else I can do or check before getting into the carburetor.

Any ideas?

  • 3
    A bit hard to engine troubleshoot online, but I'd check the idle springs on the throttle body. They'll do pretty much exactly what you described if they stretch out.
    – Comintern
    Commented May 15, 2015 at 4:21
  • Thanks. Are those springs also called the governor?
    – user26270
    Commented May 16, 2015 at 0:02
  • 2
    The governor is typically a vane that gets blown by airflow from the flywheel - the governor spring is what tensions it against the throttle.
    – Comintern
    Commented May 16, 2015 at 0:06
  • Thanks, that was it! Just had to adjust the tab that the spring was attached to. Throttled up nicely.
    – user26270
    Commented May 16, 2015 at 2:13
  • Glad that did the trick. I'll post it as an answer so it doesn't wind up where comments go to die.
    – Comintern
    Commented May 16, 2015 at 2:15

7 Answers 7


In my experience, unless the engine is running roughly idle problems are usually related to the throttle and governor.

From your description, it sounds like you may have a problem with the governor spring that tensions the governor vane to the throttle body. These can get stretched out and lose tension creating a slow idle.


Check the brake / coil cut off safety mechanism. I've had some strange-running issues that seemed to be related to the safety-brake mechanism dragging, and/or squirrel/mouse electricians partially-connecting the shutdown wire to ground with their nesting material. Since the latter cuts off spark it might have the effects you mention. Nest material not being a particularly good conductor it's rarely the full-shutoff, but weak spark, yes.

Could also be a bad spark plug wire (cracked insulation) leading to weak spark.


My mower did that, then finally quit. Come to find out it was my camshaft. The exhaust lobe was worn-out. Wasn't letting my exhaust value open. Or, check the rocker arms. Valves might need adjusting.


One other thing that I would hope every one would think of but not dumbie me is to make sure the blade well of your mower is cleaned out now and then...my mower would start and run fine tell you started mowing,then would bog down and die,even in short grass. Cleaned air filter,checked and cleaned calibrator, still to no avail.turned mower over to make sure no obstruction, cleaned out well..now runs great


On my mower (Craftsman 247.37037 with Briggs & Stratton engine), it was a matter of replacing the choke thermostat -- it wasn't sensitive enough any more to fully push the air vane forward. It requires removing the blower housing and cover and the muffler, but takes less than 20 minutes and cost me about $15. https://www.youtube.com/watch?v=Z3XP5mz59mA

  • Well, it turns out that the mower ran for only a little while before dying again. I took off the carburetor and it was pretty clean except the fuel intake was clogged with fibers -- probably dog hair. I cleaned it all out and it's running good as new. Hopefully, this is the real solution.
    – Goldie
    Commented May 10, 2018 at 19:44

If the carb has been worked on the carb levers need to be in the correct position, especially with the governor lever.

  • 2
    Hello, and welcome to Home Improvement. You seem to have stopped halfway through your answer; would you edit and complete it? And, you should probably take our tour so you'll know how best to contribute here. Commented Sep 17, 2019 at 15:19

I had the same problem. Found the solution by watching this video: https://www.youtube.com/watch?v=HveZoY5ddVM

  • Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. Commented Oct 12, 2016 at 11:07
  • I see. I'll remember for next time, thank you. Commented Oct 17, 2016 at 3:08

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